A bidding box is a device used for bidding in bridge, usually in duplicate bridge competitions. Made in various configurations and sizes, it is typically a plastic box with two holding slots, each containing a set of bidding cards: one with 35 cards with symbols of bids, and the other with cards for other calls (pass, double, etc.).
Invented in Sweden in 1962, they were first used at a World Bridge Championships game in 1970. Their usage eventually spread in Europe, United States and around the world, and today they present a virtually indispensable piece of equipment even for home-played games.
Use of bidding boxes has several advantages over oral bidding: it reduces noise in the room, prevents bidding being overheard at neighboring tables, allows easier review of the auction, and reduces the opportunity to pass unauthorized information to one's partner (intentionally or not) by the manner and intonation in which one makes one's bid.