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Hands Evaluation by Opening Points

What exactly are opening points? At bridge classes we used only High Card Points. 


The problem of defining the strength of hands just in terms of high card points (HCP) is that distribution is not measured unless extra points are added for long suits or shortages. Some of the difficulties can be overcome by utilising the concept of Opening Points (OP). This style of evaluation is particularly effective in defining the strength of opening bids. The calculation requires adding the number of HCP in the hand to the sum of the number of cards in the two longest suits. Here are four examples.


Hand 1


  A J 8 7

  6 2

  K Q 9 3 2

  8 6

High Card Points (HCP) =10; Sum of number of cards in two longest suits =5+4=9.

Opening Points (OP) =10+9=19.

A majority of Acol players normally regard 19 OP as the minimum for an opening bid.

Some players might pass on this hand with its 10 HCP. Others might open One Diamond. 


Hand 2 


  K 8 7 2


  A 10 3

  Q J 7 4 2

High Card Points (HCP) =14; Sum of number of cards in two longest suits =5+4=9.

Opening Points (OP) =14+9=23.

With its value of 23 OP, this is a sound opener of One Club.


Hand 3


  A Q J 7 3 2

  A 2

  A K 9 6


High Card Points (HCP) =18; Sum of number of cards in two longest suits =6+4=10.

Opening Points (OP) =18+10=28.

With 28 OP this hand is worthy of a traditional Acol Two Spade opener.


Hand 4


  A K Q 4 3 2 

  A 4

  A K 

  K J 5

High Card Points (HCP) =24; Sum of number of cards in two longest suits =6+3=9

Opening Points (OP) =24+9=33

With 28 OP, this is a very powerful hand. An artificial Two Clubs is the standard Acol opener.


Full details can be found in section 5 of the 2019 edition of the EBU Blue Book. 


Mechanical Errors


Would you explain Mechanical Errors please?

The majority of bridge players generally welcomed the introduction of bidding boxes. Not only does their use remove unfortunate voice inflection from the game, but in addition the bidding process becomes easier to comprehend with the coloured cards clearly visible around the table.

Nevertheless a certain degree of confusion followed their adoption, particularly in relation to removing an unintended card from the bidding box, known colloquially as a mechanical error. The onus is mainly with the bidder, who should check the card before its removal, but inevitably errors occur from time to time. The removal of a card next to the one intended is common. Bidding cards can easily stick together as they become worn and a lower bid can mistakenly be made. In like manner a player temporarily flustered perhaps by an unusual auction or an opponent’s question can pick out an unintended card such as alert or double.

Take this sequence of events in the incomplete auction:

South              West               North              East

1H                   2H (1)              Pass                                        (1) alerted by East

South opens One Heart. West puts down the stop card and thinks he bids Two Spades. In reality he plays the Two Hearts card. North passes just as East alerts with the blue card from his bidding box. West is clearly surprised by the alert, as his overcall is weak and natural with a six-card spade suit. He looks down and sees that he had pulled out the Two Heart card rather than the Two Spade card. He explains that he meant to bid Two Spades and not Two Hearts. North rightly calls the TD who examines West's hand. He rules that as West intended to bid Two Spades, the Two Heart card was a mechanical error and West can change the bid to Two Spades. North objects as he claims he has already passed.

The TD explains that if East had made a call before West had spotted his error, the mistake cannot be rectified. However, if a player discovers that he has not made the call he intended, he may, until his partner makes a call, substitute the call he intended for the unintended call. The intended call of 2S by West now replaces the erroneous 2H call.

South then complains that East has only spotted the error because of partner’s alert of the Two Heart bid (which systemically indicates a two-suited hand with opening values). The TD explains that this fact does not affect his decision as under the same law a player is allowed to replace an unintended call no matter how he may have become aware of his error.

The director then goes on to explain that North can withdraw his Pass and substitute another bid. Any implication from North's replacement bid is authorised for South but not for East-West. The bidding then continues in sequence with East to call.

The TD may also note that West’s use of the stop card adds credence to his claim that he meant to bid Two Spades (and not Two Hearts). It is obviously easy to say that West could have avoided the situation by double-checking his bidding card as he removed it. Even so nearly every player will have experienced this problem and made a similar mistake.

Full details can be found in Section 25 of the 2017 laws.

It doesn't seem fair

Question:  My hand was a 22 count and I was so delighted that I opened it with a strong natural game invitation bid of two spades.  Unfortunately the opposition pointed out that my partner was dealer.  The TD ruled that if my LHO wished to let the bid stand then the bidding could continue from there.  However my opponent did not condone my bid, so the opening bid reverted to my partner.  Partner passed, but my RHO bid a weak two hearts.  I bid two spades again which was passed out.  I made twelve tricks for a poor score.  Now, does that seem fair?

Well, no one made you bid out of turn; it was your error albeit in the excitement of holding a good hand.  To avoid the problem, each time you remove your cards from the board get into the habit of checking the vulnerability and the dealer.  Now let’s look at the basic scenario.  The LHO can condone the opening bid out of turn, and the auction can continue without penalty.  However the opponents declined that option. 

It was for your partner to open.  Your call was cancelled and the bidding reverted to your partner who now had Unauthorised Information (UI) regarding your spade suit.  (There may have been lead penalties involved if the auction ended with your opponents playing the contract.  That situation did not arise here.)  The auction started with your partner’s pass.  Your RHO then made a weak two bid in hearts, say 5-9HCP.  By repeating your two spade bid you now suggested that you held the values for an intermediate spade bid, but the three other players knew you had a strong hand, Your partner could not make use of that information so ethically passed. 

Here is an alternative line.  You have a 22 count with six spades.  This means there are 18 points between the other three players.  Why not take the view they are divided six, six and six.  With your 22 count and partner’s six, you have a possible 28 points between the hands.  Go for it; bid game in spades.  So the auction could have gone:

North (Dealer)             East (RHO)                 South               West (LHO)

Pass                            Pass                            4S (You)          All Pass

Perhaps you feel really lucky and bid six spades instead of four.  After all, your partner may have up to 11HCPs.  On this occasion fate had it that you received a bad score.  Bridge is like that. 

By the way, the TD can award an adjusted score if your partnership has gained unfairly from the original Bid Out of Turn. 

The full account of Calls out of Rotation can be found in sections 25 and 28-34of the 2017 Laws, good bed time reading – especially for an insomniac! 

The Duties of a Dedicated Dummy

Most players believe that being Dummy is rather boring and try to avoid the role as the main duty is to place played cards in the direction of NS or EW depending on who won the trick. However the number of rights and constraints thrust upon you may surprise you. Here are just some of them.

As Dummy you can:

1. Warn any of the players that a quitted card is in the wrong direction, but only if you spot the lapse before the next trick is started.

2. Attempt to prevent Declarer leading from the wrong hand by saying something like, ‘I think you are in Dummy’. However you must not point out the error once a card has been played.

3. Try to prevent a Defender from leading out of turn. Even so you must remain silent once the card has been played.

4. Attempt to warn Declarer of a possible revoke by for example asking, ‘No more spades, partner?’

But what about the limitations placed on Dummy?  Once again here are just a few of them.  During the play of the hand, as Dummy you are not allowed to:

5. Comment on any irregularity committed by any player.

6. Study an opponent’s system card.

7. Say how many tricks have been won or lost.

8. Call the TD on your own initiative.

9. Hover over a card or suit in dummy in anticipation of declarer’s next play.

At the end of the play of the hand as Dummy you may:

10. Draw attention to a perceived irregularity.

Condition 6 is often broken at club level. The danger here is that you may unintentionally be giving unauthorised information (UI) to your partner.

Condition 9 is quite important.  At one time or another, I suspect most of us have committed this offence in an attempt to save time. However it is prohibited under the laws. The TD can award an adjusted score if he/she believes that Dummy was indicating a possible line of play to Declarer.

Technically a procedural penalty against your side is a possibility for disregarding any of the rules, but in club competition the TD would probably just point out your error and take no further action. 

Note: The list above is not exhaustive; full details can be found in Sections 42-43 of the 2017 laws.

Opening Leads Out of Turn

Question:  After a perfectly ordinary auction, an opponent made an opening lead out of turn. As declarer I tried to stop her, but we all saw the card and I called the director. The TD explained the options to me, but I found them difficult to understand. Can they be explained simply?

The Laws require that the opening lead be placed face down on the table. The player should ask, ‘Any questions, partner?’ If partner replies, ‘Yes, why are you putting down a card? I’m the one supposed to be on lead’, then the card can be returned to hand without penalty. The real opening leader should then ask, ‘Any questions, partner?’ and hopefully the answer will something like, ‘No questions, partner. I do apologise for my careless behaviour a moment ago. Next time I will be more careful. Thank you for being so understanding.’ Well, OK, so I live in a Utopian dream world. It must have been those special mushrooms I ate at breakfast.

Assume the wrong Defender makes a face-up lead. You as Declarer, whether intentionally or not, can face your cards as dummy and your partner becomes Declarer and plays the hand.

If you do not want to be Dummy as Declarer you first choose one of two actions:

1. Accept the lead or

2. Reject the lead.

If you accept the lead (Action 1), then Dummy is faced on the table, you play from hand next and the board is played out in the usual way.

If you reject the out-of-turn lead (Action 2) and require your left hand opponent (LHO) to lead, you then need to decide on one of three options.  They are:

a. Ask your LHO to lead the same suit erroneously led by your right hand opponent (RHO) who then places the offending card back into hand. (If LHO has a void in that suit, any card may be played as a replacement.)

b. Ask your LHO not to lead the same suit as erroneously led by your RHO who then places the offending card back into hand.

c. Allow your LHO to lead any card. The RHO’s offending card now becomes a penalty card and as such stays on the table until played at the next legal opportunity.

You as declarer have an absolute right to choose the approach, which appears to benefit your partnership.

Beware of this related situation.  Suppose a North-South partnership is in a contract. East leads face down and South faces his cards before he remembers that he is Declarer. Since East correctly did not expose the card, it may be withdrawn without penalty and West must lead.  Of course Declarer, South may still pick up the faced cards, but the opponents now have the advantage of having seen them!

Full details on Leads-out-Turn can be found sections 53-59 of the 2017 laws.

Interpreting Bridge Speak

Question:  When players at the club explain the auction to me they often use terms I don’t quite understand.  Puppet and Relay are two that spring to mind.  What exactly are they? 

When discussing systems experienced players are often content to talk in Bridge Speak as a sort of shorthand.  Unfortunately the terms they use can be incomprehensible to others.  Puppet and Relay bids are mainly used as responses to a range of conventional bids, but let’s start at the beginning. 

An Artificial bid is one that is not natural and which, by agreement, carries a coded meaning not necessarily related to the denomination.  A Convention (usually given as a familiar name) is an agreement about any artificial call or bid, with a set of related calls, which are assigned meanings by partnership agreement that may or may not relate to the denomination bid.  Thus Stayman 2C over 1NT and Blackwood 4NT asking about aces are both conventions. 

A Forcing Bid is any bid that compels partner to take further action.  Suppose opener bids a natural 1H.  In traditional Acol the next player might use an artificial cue bid of 2H to show a strong hand.  The 2H bid is clearly forcing.  In other versions of Acol, a 2H bid may be used instead to show a two-suited hand such as spades and a minor.  In both cases partner is expected to keep the bidding open.

A Relay Bid is a term for an artificial bid that usually has little or no descriptive meaning but asks partner to describe some feature of their hand in response.  A relay is often the cheapest bid available.  The descriptive response can be natural or coded.  For example, after a 2C opening bid in traditional Acol, a response of 2D is often used as a negative relay to show limited values. 

A Puppet bid is a particular relay that usually requests partner to make the cheapest bid regardless of his hand.  For example, after an opening bid of 1NT an opponent may come in with a natural 2H bid. Playing the Lebensohl convention, opener’s partner bids a conventional 2NT that requests partner to bid a puppet 3C, which may be partner may pass or convert to another suit at the three level to play as a non-forcing weak takeout

An Asking Bid is a request for information about a feature of partner's hand, such as the number of controls, suit length, or control of a particular suit for a possible no-trump contract.  In the sequence: 1H – 2C – 2D – 2S, the 2S bid is often used as Fourth Suit Forcing (FSF), a conventional asking bid used to discover whether partner holds a stop in spades for a No-Trump contract. 

Is your head spinning? If so I apologise; it's no surprise.  What is clear however is that most of the Bridge Speak terms overlap in their meanings, so there is often confusion as to which one to use.  Don’t worry about it.  Don’t be afraid to ask a supplementary question if you are confused by opponents’ explanations.  Even so please remember that if you do not require information during the auction, then it is better to wait until the clarification period, just before the opening lead is faced. 

If you are asked the meaning of any of your partner’s bids, simply do your best to explain them without any technical jargon. 

Comparable bids in action

Question:  In your article on the new laws you mention comparable bids.  I think I understand the principle, but could you give some examples please. 


When an insufficient bid or a bid-out-of-turn is made, the director should be called immediately to safeguard your rights and those of your opponents. The left-hand opponent can condone the errant bid in which case the auction continues without penalty, but what happens if the opponents decline that right? 


The new laws are more liberal to the transgressor than previously.  In the illustrations we will assume that both pairs are playing a four card natural system such as Acol: 


1. Let’s take insufficient bids first.

A. If the bid is natural and the lowest sufficient bid in the same denomination is natural, the player can correct to that bid.  There is no penalty and the bidding continues in sequence. 


Ex1.                 West               North              East                South

                        1 H                  Pass                2H                   1S


South can correct 1S to 2S and the bidding continues.  2S is considered a comparable bid.


B. If there is an alternative call, which means the same as the insufficient bid, or is contained within the meaning of that bid, the player can correct to that call.  There is no penalty and the bidding continues in sequence. 


Ex2.                 West               North              East

                        1 D                  1S                    1H


If the system played by East-West uses a negative double to show hearts, East can correct 1H to double

Ex3.                 West               North              East                South

                        1H                   Pass                3H                   Pass

                        4N                   Pass                4C


If the TD is satisfied that East intended to answer 5C in response to Blackwood, but bid at the wrong level, then East can correct 4C to 5C


Ex4.                 West               North              East

                        2N                   Pass                2H


If 2H was intended as a transfer to spades and 3H is also a transfer to spades over 2N, then East can correct 2H to 3H


2. Now take the case of a bid out-of-turn. 

Ex5.     East passes out-of-turn when West is dealer. 


                        West               North              East

                        1H                   Pass                2H


This sequence is allowed, as the 2H bid is natural (say 7HCP) and East would have been passed as opener.


Ex6.     East passes out-of-turn when West is dealer. 


                        West               North              East

                        1H                   Pass                1S


The bid of 1S is not allowed, as it is could be unlimited (say 14HCP).  Because East has already passed, West knows that East holds less than values expected for an opening bid.  It is not a comparable bid.  The TD will explain the options at the table.    


Ex7.     West opens 1NT and East bids 2D (transfer to hearts) before North calls.  The bid is not condoned and North bids 2S. 


                        West               North              East

                        1NT                 2S                    3H


3H is allowed, as it is has a similar meaning to the 2D transfer bid and can be considered comparable.  

New Laws of Duplicate Bridge 2017

Question:  I heard that new laws of bridge have been introduced worldwide.  I haven’t seen much publicity.  How will they affect me at the club?  I don’t usually play at county events. 

Traditionally a full revision of the Laws of Duplicate Bridge takes place approximately every ten years.  The last Red Book was produced in 2007.  Now the latest version (no longer red) has been published, and came into effect for EBU events in August 2017.  From a player’s point of view, there are no changes to the mechanics or scoring of the game.  Hence you can essentially continue to play your familiar game and allow the Tournament Director to worry about dealing with any irregularities that arise.  However there are a couple of changes, which might interest you. 

Change to Laws regarding Claims and Concessions

If a claim or concession has been made, play need not be suspended if the non-claiming side suggests playing on and if all four players agree.  In this case the outcome at the table will be final and the TD will not be involved. 

Change to Laws regarding Calls out of Rotation and Insufficient Bids

This change introduces the comparable call.  This is a call that the TD allows as a replacement for a withdrawn call, if it:

1. Has the same or similar meaning as that attributable to the withdrawn call, or

2. Defines a subset of the possible meanings attributable to the withdrawn call, or

3. Has the same purpose (e.g. an asking bid or a relay) as that attributable to the withdrawn call. 

This is similar to the existing idea for allowing replacement bids for insufficient bids, but it has been more explicitly explained and its application has been extended to calls out of turn.  In most instances, replacing an insufficient bid or a call out of rotation with a comparable call will allow the auction to continue smoothly and fairly.  Do note however, that if you appear to have gained by an insufficient bid or a call out of turn, the TD has the authority to award an adjusted score. 

Other Changes

There are quite a few technical amendments within the new laws.  For example there is a minor revision to the process of penalty assessment following a second revoke on the same board.  There has also been a post-publication clarification regarding lead restrictions.  However in general terms, any judgement relating to these situations can be left to the TD. 

If you feel you require additional information then go to the EBU website,  Click on the laws and ethics button in the sub-menu on the right hand side of the home page.  There you will find details and examples of all the law changes together with the updated EBU playing regulations. 

Most importantly, do not fret.  Life at the bridge table will appear unchanged.

A Cautionary Tale of a Claim by Declarer

Question:  Over the years I have made many claims as declarer without any problem, but can recall an occasion when a defender challenged my claim and became quite abusive about it, so I can see why many players prefer to see the hand played out in full.  In your web article, Claims by Defender, you seem to imply this approach is unacceptable.  Do I understand you correctly? 

Like you I have found that most defenders, after listening to declarer’s statement in regard to the line of play, will peruse dummy and declarer’s hand and accept the claim gracefully.  Inevitably sometimes a further clarification is required.  However if there is a problem and the defenders do not accept the claim, then under Law 68D the TD must be called immediately and will arbitrate on the validity of the described play.  No defender has the right to be abusive and the director should address that as a separate issue under the EBU Best Behaviour at Bridge guidelines. 

For newcomers to bridge at club level, it could be argued that it is acceptable to play out hands in full on the grounds that that they do not yet have the experience to make a claim.  Unfortunately this approach is not the expectation at county or higher levels.  As newcomers become more experienced they should gain the confidence to make claims at increasingly earlier stages in the play.  This will avoid the possibility of evoking Law 74B4 concerned with prolonging play unnecessarily. 

Of course if all players stuck to the laws, rules and regulations of bridge many problem areas could be eliminated.  In the following scenario below, how many infractions can you identify? 

West was on lead when South, the declarer, said, ‘I have the rest of the tricks.’  East protested as he had a trump left.  South then explained that he had a high enough trump to draw it once he was in.  West intervened with, ‘What if I lead this,’ and led a club, which West (but not declarer) knew that East could ruff.  Declarer hesitated, but now realizing that East might be void and could probably ruff this trick, ruffed high, before proceeding to draw the remaining trump. 

OK?  Now how many infractions and problem areas did you spot?  Here are at least some of them. 

  1. Declarer should have stated a line of play when he claimed. 
  2. Then all play should have stopped. 
  3. On East’s protest the director should have been called. 
  4. West should not have shown the club card to the other players. 

If the Director is called immediately, under Law 70, he would instruct all players to face their cards.  The director asks declarer to repeat the line of play he stated at the time of the claim.  Since declarer did not give a line of play at that point, it is too late for him to do so now.  West or East can now suggest a possible play by declarer, which might be ‘careless or inferior’, but not ‘irrational.’  West suggests a club lead for East to ruff.  The TD is likely to rule that declarer ruffs low in dummy thus allowing East to over-ruff and win the trick.  The director now awards this trick to the defenders since ruffing low qualifies as ‘careless or inferior,’ (Law 70D) and also because ‘any doubtful points shall be resolved against the claimer’ (Law 70A). 

Full information on claims and concessions can be found under Laws 68-71 and Law 74.

Claims by Declarer

Question:  As a relatively inexperienced bridge player I have never made a claim at the bridge table and as declarer I always play the hand out to the last card.  The other day an opponent asked why I didn’t claim earlier in the play when I only had winners left in my hand.  I explained that I thought it safer to play out the hand in case I made a mistake in describing my intentions.  To be fair the opponent didn’t make an issue of it.  But I would like to know about the etiquette involved, and also the pitfalls in making a claim, particularly an erroneous one. 

Firstly let’s look at etiquette.  It is generally accepted, that to avoid slow play, a declarer should claim or concede when sure that the remaining tricks are either all to be lost to the defence or all to be won by declarer.  To save time experienced players will also make a claim when conceding some of the tricks but making others.  Your current approach is not ideal and I think you should definitely make a claim when either your hand or your dummy contains only winners.  However I suggest that for the moment you continue your current practice if you are uncertain of how to explain your intentions particularly when there is a need to switch to and fro between dummy and the closed hand.  Hopefully with increasing confidence, you will soon feel comfortable enough to start making more complex claims. 

Now for the procedural aspects and some pitfalls.  Once a claim is made there are two main points to note under Law 68C.

  1. All play ceases.
  2. Declarer shows the closed hand and announces how the remaining cards are to be played.

If defenders accept the claim then the board is scored in the usual way.  On the other hand if the opponents contest the claim, under Law 68D the TD must be called and will arbitrate on the validity of the described line of play.  Under EBU guidelines for example, the director will assume that a solid suit would be played from the top, but that any card could be chosen from a broken suit.  According to Law 70A, the TD must be fair but give any benefit of doubt to defenders. 

When trumps are not mentioned in the original claim, there is a general misconception that if one or more trumps remain with opponents, the latter pairing will automatically be awarded at least one extra trick.  Under Law 70C this is not always the case.  For example suppose a declarer makes a claim and states that s/he will win the four remaining tricks on a crossruff.  If all trumps remaining with defenders are lower in value than the four held by declarer and dummy then the claim will still be valid as the opponent trumps will be smothered by declarer’s larger ones.  Nevertheless it is wise for declarer to describe the intended procedure for dealing with any trumps lurking with defenders so that all ambiguity can be avoided. 

There is another common misperception namely that a defender has the right to suggest defence to partner once the declarer has exposed the closed hand.  As the Yellow Book notes, either opponent can:

 ‘Challenge the claim, and then explain to the director plays that exist which would invalidate the claim.’

Full information on claims and concessions can be found under Laws 68-71.

Dealing with an Infraction by Dummy

Question:  I thought that if declarer played a card when dummy was on lead that dummy could point this out and declarer could then replace the card (assuming LHO had not played a card) and lead from dummy without any penalty.  Do you know what the exact position is?

Law 42.B.2:on dummy's qualified rights is specific in that it states:

'Dummy may try to prevent any irregularity by declarer.'

However there is an important caveat under law 43.A.1.b on dummy's limitations namely:

'Dummy may not call attention to an irregularity during play.'

In other words dummy may try to stop declarer playing from the wrong hand, but once declarer has nominated or shown a card that card is played and dummy must not comment but remain silent.  In the case you cite, dummy is now subject to law 90 and the TD can impose a procedural penalty on dummy.  In a club pairs event this would normally be a warning for a first offence (and perhaps a penalty for any second occurrence later in the session).  Specifically under law 90.A:

'The director ... may assess procedural penalties for any offence that ... violates correct procedure.'

So far defenders are not involved but now the laws which deal with declarer's lead out of turn becomes relevant and law 55.A states:

'...either defender may accept the lead .... or require its retraction ... If the defenders choose differently the option expressed by the player next in turn shall prevail.'

Law 55.B.2 clarifies that in general no penalty is imposed on declarer:

'... if either defender require [declarer] to retract the lead, he withdraws the card led in error.  He must lead from the correct hand.'

Law 55.C notes that in exceptional circumstances:

'When declarer adopts a line of play that could have been based on information obtained through the infraction the director may award an adjusted score.'

Full information can be found under Laws 42, 43, 53, 54,55 and 90.

Asking Questions

Question:  In your article on Unauthorised Information you explain why one should be circumspect as to when and how to ask about an opponent's call.  Have you any advice on how to phrase questions to minimise such risks? 

Remember that opponents should have fully completed system cards available to show the basics of their bidding style.  Perusing these can often avoid the necessity of asking at all.  Unless you need to know at once, it is wiser to wait until the end of the auction before asking questions as this minimises the possibility of passing unauthorised information (UI) to your partner.  In particular, avoid influencing partner's lead by waiting until the face-down card is on the table in the clarification period. 

I suggest you try to phrase any inquiry in a neutral manner by simply requesting an explanation of the auction or a particular call.  For example, when inquiring about an alerted 3♣ bid, it is better to ask, ‘What does the 3♣ bid show?’ or 'How do you play 3♣ in this situation?' rather than ‘Is that Stayman?’ or 'Is that a transfer bid?'  Only if further clarification is needed should specific questions be asked.  General questions such as, ‘Is that bid weak?’ or ‘Is that forcing?’ should be avoided as this style of phrasing often receives simple one-word answers which may be incomplete.  Similarly, the use of the words ‘standard’ or ‘natural’ in questions sometimes leads to unhelpful responses.  In complex auctions it is reasonable to ask for an explanation of the entire auction before the opening lead is faced.

Take the following sequence with only opponents bidding:

            North              East    South              West

            2C (alert)         Pass    2D (alert)         Pass

            2NT                 Pass    3C (alert)         Pass

            3S                    Pass    3NT                 End

Before making an opening lead it is perfectly reasonable for East to check the meaning of the alerted bids perhaps by asking something like, 'Could you just take me through the auction again with explanations, please?'  This might result in a description such as:

            '2C is either game forcing or a super strong no trump;

            2D is an artificial relay;

            2NT is 23-24 HCPs;

            3C asks for four card suits to be bid in ascending order;

            3S shows precisely four spades;

            3NT is to play.' 

No one could possibly object either to the defender's request or to the precise explanation by opponents. 

In summary, asking questions about a specific call may give partner information which can constrain subsequent calls, leads or play.  If at a player’s turn to call there is no need to have opponents' calls explained, it is in the partnership interest to defer questioning until the opening lead.  Incidentally, a player must not ask a question as a method of drawing partner's attention to the meaning of an opponent's bid. 

Full information can be found under Laws 16 and 20 together with associated material in Laws 40, 41, 47 and 75.