Grand slam force Grand slam force The Grand Slam Force is a bidding convention in contract bridge that was developed by Ely Culbertson in 1936. It is intended to be used in cases where the combined hands of a partnership are so strong that a slam (winning at least 12 tricks) is a near-certainty and a grand slam (winning all 13 tricks) is a possibility. It allows one partner to gain information on the quality of trumps in the other partner's hand. When this convention is in force, a bid of 5NT (five notrump), when it does not conflict with other conventions used
Bidding system Bidding system A bidding system in contract bridge is the set of agreements and understandings assigned to calls and sequences of calls used by a partnership, and includes a full description of the meaning of each treatment and convention. The purpose of bidding is for each partnership to ascertain which contract, whether made or defeated and whether bid by them or by their opponents, would give the partnership their best scoring result. Each bidding system ascribes a meaning to every possible call by each member of a partnership, and presents a codified language which allows the players to exchange information