Bidding box 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. A bidding box is typically a plastic box with two slots, each containing a set of bidding cards. One slot contains 35 cards with symbols of bids (5 denominations—clubs (), diamonds (), hearts (), spades (), and notrump (NT)—in seven levels of bidding,
Bidding box placed over the bidding cards attaching to the box base. A bridge auction consists of a sequence of "calls" (a bid, pass, double, or redouble) made by each player in turn, until it is concluded by a sequence of three consecutive passes. With the transition from auction bridge to modern contract bridge, the bidding has become more complex, and conventional auctions often last through several rounds of bidding. Such long auctions are hard to memorize and review. In addition, oral bidding causes noise in tournament halls, and auctions can be easily overheard at the other tables. Bidding boxes were invented