In auctions where opener has bid a suit, responder has bid a second suit and opener has rebid in a third suit, responder can often find himself in some difficulty if he has values to invite game or force to game. If he can support either of opener's suits, he can do so by raising to the appropriate level. If he has a good stopper in the fourth suit, he can bid no trumps at an appropriate level, depending on his strength. But he may be able to do neither of these. A simple rebid of his own suit shows a weak hand and a long suit, so that is out, especially since it suggestss a misfit and will very likely end the auction. A jump rebid promises a good long suit and responder's suit may not meet that requirement. So what can he do?
Modern bidding has the answer: Forth Suit Forcing. Responder simply bids the fourth suit, which says nothing particular about his own holding in the fourth suit and is a request for opener to provide more information.
Opener's first choice is to bid no trumps if he has a stopper in the fourth suit. He should bid 2NT (if able) with a minimum, which responder can pass, otherwise 3NT.
With 5 cards in his second suit, opener should rebid his second suit.
This tells responder that he is
If opener has no stopper and no extra length in his second suit, he rebids his first suit. This does not promise extra length (because opener has been forced to make a bid), although he may, of course, have extra length.
Responder will often know enough to pick the final contract.
If he had been angling for 3NT but has found a stopper missing,
he might choose to try a
Sometimes, though, responder may have bid the fourth suit for other reasons. He may just have needed to set up a forcing auction in order to make a suit bid that would otherwise have been non-forcing. He may even have a genuine holding in the fourth suit. If responder bids a suit below game after having used fourth suit forcing, this bid is also forcing.
Author: Chris Burton
Gravesend Bridge Club