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 six, so a bid must be between one (seven tricks) and seven (thirteen tricks). A bid is higher than another bid if either the level is greater (e.g., 2 over 1NT) or the denomination is higher, with the order being in ascending order: , , , , and NT (no trump). Calls may be made orally, or with a bidding box, or digitally in online bridge. If the last bid was by the opposing partnership, one may also the opponents' bid, increasing the penalties for undertricks, but also increasing the reward for making the contract. Doubling does not carry to