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 box in 1962 in Sweden by Gösta Nordenson and first used at a World Bridge Championships game in Stockholm in 1970. Eric Jannersten, a Swedish social bridge player and founder of the largest European bridge equipment manufacturer, Jannersten Förlag AB bought the patent in 1970 being attributed by some as the inventor. However, the patent is disputed by the Swedish Bridge Federation. They quickly became popular in Europe, and after some resistance were accepted in American bridge clubs. , they are practically an indispensable part of the game, and even many rubber bridge players use them at home. Use of bidding