Contract bridge grand slam exists. The modern game of contract bridge was the result of innovations to the scoring of auction bridge by Harold Stirling Vanderbilt and others. The most significant change was that only the tricks contracted for were scored below the line toward game or a slam bonus, a change that resulted in bidding becoming much more challenging and interesting. Also new was the concept of "vulnerability", making sacrifices to protect the lead in a rubber more expensive. The various scores were adjusted to produce a more balanced and interesting game. Vanderbilt set out his rules in 1925, and within
Contract bridge (a union of the ABL and the USBA), and it remains the sanctioning body for bridge tournaments in North America. In 1958, the World Bridge Federation (WBF) was founded to promote bridge worldwide, coordinate periodic revision to the Laws (each ten years, next in 2017) and conduct world championships. In tournaments, "bidding boxes" are frequently used, as noted above. These avoid the possibility of players at other tables hearing any spoken bids. The bidding cards are laid out in sequence as the auction progresses. Although it is not a formal rule, many clubs adopt a protocol that the bidding cards