Switch

The BBO window on the left is the most common auction and result, including my friend. The one on the right is mine. Several pairs reached 4♥ as shown in the middle. You can step through the deal just as if you were on the BBO site, to see the play and final result.

- Hey John, that 2NT bid on board 12 was pretty gutsy!

- Not really - not playing switch.

- Switch? Never heard of it!

- Marty Bergen described it in a Bridge Today article in 1995, and I have spent 25 years wondering why it never became popular. The basic idea is that after North overcalls an opening by West we want North, not South, on lead, so all bids by East are essentially transfers. The double was a sort of transfer to notrump.

OK, so these tables need a little explanation. The top left box describes the situation: here West has opened 1♥ and North has bid 1♠: East is deciding what to do. (We are always EW. West normally bids first.) Inside most boxes are the requirements for that bid: first the length restrictions in relevant suits, and then the point count. The table says that with 0-5 points, East should either pass (denying three hearts) or bid 2♥ (promising three). This distinction can be critical if West has to decide how high to compete. West will also be happy to know that in defence from AKxxx he can be sure of cashing two honors and getting a ruff.

It is very logical: every bid is designed to keep South off lead.

• Raises keep North on lead, so they are natural and preemptive
• The cheapest bid (double) shows lack of fear of further competition.
• 1NT says the deal will probably not be played in NT. The only time East can be confident of this is when he has ♥ support. 2NT says also that both sides can probably make 9 tricks according to LoTT.
• 2♣ says the deal will probably not be played in ♣: ♦, ♥, or NT are still likely.
• The cue-bid says anything is possible.

Keeping South off lead adds about a third of a trick on average to your expected result. In this case, it added four tricks, as you can see.

Because East can show diamonds even with a weak hand, West must be careful with his next bid. This makes the descriptions of the first two bids rather optimistic: much of the time you will have to choose the least lie on a minimum hand. Had East bid 2♦ to show clubs he would have shown more strength, so West can bid more freely just as if East had bid a natural forcing 2♣.

Had the spade and diamond suits been reversed, the bidding would have been pushed almost a level higher. The first result is that a pass can now be made with three trumps. The only hands which do not require more strength to bid (because of the higher level) are those with clubs.

On the other hand, the double would now bring in +800 and is clearly the preferred result on this deal!

Over a club overcall, a 2♦ response is available. This could obviously be used either as a transfer to spades, or as a heart raise. I prefer the latter: I love my super-weak single raise!

The same basic strategy is used over a takeout double by North. The motivation is slightly different: an overcall tells South about a great lead; a double says North does not know what to lead, so is leaving the choice up to South. This creates a considerable incentive to discourage South from bidding, thus telling North what to lead. Fortunately, we can transfer to any suit at the two level, or make any natural preempt at the three level or higher. (There is a price to pay: 1♠(X)1NT is the only way to transfer to clubs at the two level. If you end up in notrump, South has the information to make a good lead through West. This leaves 1♠(X)2♥ to show a constructive raise.) There is little point in East bidding a four-card suit, since North is more likely than West to fit it, so showing your suit shows five. With a balanced hand with no trump support, redouble with 8+ points: you have the balance of strength and a good chance of penalizing the opponents. With the balance, you must not let opponents play undoubled - all passes are forcing. With weak hands, East suspects South has enough for a free bid, so jumps if safe. The 2NT response shows shortness in the suit opponents can do the most damage in: the highest unbid!

Doubles and suit overcalls of other one-level openings are handled the same way. Raises of minor suits always require one more trump than a similar raise of a major. Most serious players already handle interference over 1NT with transfers. A 1NT overcall by North is a little different. Sometimes North has a balanced hand and wants South to pick the lead. Sometimes North bid 1NT based on a solid minor, which South will rarely lead. There is therefore much less reason for East to play transfers in this situation. There is a better reason not to play two-level transfers over North's 1NT overcall: you might want to play in 2♣! A double is for penalties, and an overcall denies the ability to double, so it is weakish and non-forcing. 2NT has no natural meaning, so it is a good place to start three-level transfers. These must be obeyed by West! If East then passes, he is weak with a seven-suit. If he bids again, he is strong and the new bid is natural.