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,
Vanderbilt Club summary, Vanderbilt Club is: Vanderbilt distinguishes between informatory doubles and business doubles, two expressions known from auction bridge. Doubles should be informatory at the one-level; at the two-level if neither you nor your partner has previously bid; and perhaps at the three-level, depending on the player's judgment of the score and the bidding. Doubles should be made more freely in contract than in auction bridge, because the potential profit is greater. Vanderbilt does not otherwise discuss bidding in contested auctions. Vanderbilt describes three types of invitations to slam: bidding more than is needed to score game; bidding the opponents' suit;