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
Contract bridge partnership will adopt, which must be higher than the previous highest bid (if any). Eventually, the player who bid the highest contract—which is determined by the contract's level as well as the trump suit or no trump—wins the contract for their partnership. In the example auction on the right, the East-West pair secures the contract of 6; the auction concludes when there have been three successive passes. Note that six tricks are added to contract values, so the six-level contract would actually be a contract of twelve tricks. In practice, establishing a contract without enough information on the other partner's