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 system suit. Natural systems generally use opening bids as follows: The most widespread natural systems are: Various developments in the area of natural systems have resulted in systems that are natural in essence, but contain special features. Examples are systems like Romex, Boring Club, Fantunes, and EHAA (Every Hand An Adventure). Artificial systems can be further classified into: Bidding system A bidding system in contract bridge is the set of agreements and understandings assigned to calls and sequences of calls used by a partnership, and includes a full description of the meaning of each treatment and convention. The purpose of bidding