Fourth Suit Forcing

Introduced by Norman Squire. Rebid of the unbid fourth suit by responder shows that the first major suit is a 5 cards suit, besides intention to play NoTrump with minimum 11 High Card Points and asks whether the partner has stopper on that suit. It is a game forcing. The opener shows his 3 cards support to responder's first major suit if he has. Otherwise, bids NT with stopper on the fourth suit. If he does not have support and any stopper on the fourth suit he has to be more creative.  In the following auction;

Opener        Responder

1 Club         1 Heart

1 Spade       2 Diamonds

2 Diamonds is Fourth Suit Forcing, and shows 11+ HCPs and probably 5 cards of Hearts. Opener shows his support if he has 3 cards of Hearts. Otherwise bid NT with a stopper on Diamonds.

Rebid of 1 spade as the fourth suit is natural and shows 4 cards of Spades. Any jump suit could not be Fourth Suit Forcing even if it is the fourth suit. This kind of jump fourth suit shows at least 5-5 distribution and game values. Another condition for Fourth Suit Forcing is that the other three suits should be called by the partnership. So if one of the suits is called by the opponents then there is no Fourth Suit Forcing. Further, after bidding NT, 4.suit forcing does not work.