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Robin's Lesson 11-11-21
Lesson 11th November - 4th Suit Forcing

What is 4th suit forcing?

Fourth suit forcing (also referred to as fourth suit artificial;  abbreviated as FSF or 4SF) is a  bridge convention that allows responder to create, at his second turn to bid, a forcing auction. A bid by responder in the fourth suit, the only remaining unbid suit, is artificial indicating that responder has no appropriate alternate bid, remains interested in the potential for a game contract and asks opener to bid again to show additional features.

Opener responds to the fourth suit forcing by (in prioritised order):

  1. Raising responder's first bid suit with 3-card support,
  2. Bidding notrump with values in the fourth suit,
  3. Raising the fourth suit with four cards in that suit,
  4. Making the most natural rebid possible, lacking any of the above.

Fourth suit forcing is minimally forcing for one round and usually forcing to game - partnership agreement is required. Whether or not the convention is applicable if the fourth-suit bidder is a passed hand is also a matter of partnership agreement; there is no consensus amongst experts on the options as to its use being non-forcing, forcing, or forcing only after a reverse.
 
It requires an invitational hand with at least 10 points, or 12-13 upwards if it is game-forcing and opener has not shown any extra strength.

Don't forget that the 4th, suit is generally forcing to game, so no need for the bidding to rush into game - the bidding cannot stop short of game. 

Importantly, 1C  ..  1D  ..  1H  ..  1S is a spade suit, forcing for 1 round,  whilst
  1C  ..  1D  ..  1H  ..  2S is 4th suit forcing.

 

NOTE

NEVER BID 4SF WITH A VOID

If not sure what opening lead to make, when Opposition have made a 4th suit forcing bid, then lead the suit of the 4SF.
Hand 1 - Is this a suitable hand?
  1. 1♥  -  Bid up the line with 4-4 in the majors
  2. 2♣  -  1♠  would show a better hand & is forcing, so a much better bid will be to show preference for partners suit.

Opening Lead Q♥ 
Hand 2 - A 4-4-4-1 hand
  1. 1♦ -  Standard practice with a 4-4-4-1 hand with 3 touching suits is to bid the middle suit.  If you did open either a Club or a Heart any re-bid you make would either show a 5-card major, 15 HCP’s, or be a reverse.
  2. 2♥ -  4SF, forcing bid, doesn’t say West is weak in Hearts, asks Partner to further describe their hand.
  3. 3♥ -  Shows a 4-card Heart suit, but doesn’t deny wanting to play in NT.
  4. 4♥ -  Eight card fit in a major, so play in it.
Hand 3 - How would you get to game?
  1. 2♥  -  Partner has opened & so with 14 HCP North wants to be in game. He mustn’t bid 3D as although highly invitational it isn’t forcing. Not knowing the best final contract he uses 4SF & bidding must now continue until a game contract is reached.
  2. 3♥  -  South can further describe his hand secure in the knowledge that his partner will not pass.
Hand 4 and 4-4-4-1 but not touching suits this time
  1. 1NT - Don’t bid 1S as this is forcing for one round, whereas 1NT shows 6-9 points with a Spade stop.
Hand 5 - Yet another 4-4-4-1 hand
  1. 1♣  -  Second part of the rule for bidding 4-4-4-1 hands. If there aren’t 3 touching suits then bid the suit below the singleton.  Had you opened a Heart or a Spade then the singleton.  Had you opened a Heart or a Spade then any re-bid would either show 15+ points or a 5-card major
  2. 1♠  -  Fourth suit, but bid at the 1-level isn’t 4SF, just shows a Spade suit.
Hand 6 - How to get to game with this one?
  1. 3NT  -  With two Spade stops West doesn’t need to make the 4SF bid of 2S.  He knows the final contract and so bids it.
Hand 7 - An unusual openng bid!
  1.  1♥   -  If the opponents win the auction you don’t want a diamond lead.
  2. 2♠   -   4SF
  3. 2NT -  Minimum hand, with a Spade stop
Hand 8 - Takes time to find the best fit.
  1. 2♥  -  4SF
  2. 3♥  -  Four hearts

Opening lead: ♦4 – into dummy's second suit.
Hand 9 - What should responder rebid?
  1.  2♥   -  4SF, just in case partner has a 4-card heart suit.

Opening Lead: ♥4
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