Fourth Suit Forcing is used by the responder to establish a game force. So, after, say, 1-1-1, a bid of 2 is the 4th suit. Any time the auction starts: 1 grape-1 apple, and opener bids a 3rd suit, responder can bid the 4th suit (artificially) to set up a game force.
I recommend that the 4th suit is 100% forcing to Game. Example:After 1-1-2, responder holds: A Q 4 3 2 4 Q 3 2 A K Q 2. He bids 2 to set up a game force. The bid says absolutely nothing about the fourth suit. It could be xxx, it could be AKQ. The opener will usually bid notrump if he has the 4th suit stopped. Both players assume the 4th suit is unstopped until either player bids notrump.
Fourth suit forcing is typically not used after a 2/1 GF response. The 4th suit would be natural in that case (1-2-2-3=clubs).
Fourth-Suit is NATURAL and non-forcing by a passed hand (P-P-1-P-1-P-2-P-2 = 5-5 or longer in /). If the opponents have made an early double, 4th suit forcing is still on. If they overcall, it is off.
The opener bids naturally. He should have a stopper in the 4th suit in order to bid notrump. He is allowed to take a preference to responder's first suit with honor-doubleton.
Example hands for opener after: 1-1-2-2:
Bid 2NT (hearts stopped)
Bid 2 (this does not show 3-card support)
Bid 3 to show 5-5
Opener can jump raise responder's first suit with three cards and a maximum, such as: K Q 10 7
K 3 2
A Q J 4 3
(after 1-1-1-2, jump to 3).
For Advanced players: See also XYZ.
Fourth Suit forcing is alertable.
Last updated: June 2012