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,
Jump bidding will always win the item for free. Such cooperation could be very beneficial to both bidders in the long run. The problem is, it cannot be enforced, because both bidders have an incentive to say that their value is higher than it really is. Here jump-bidding comes into play. It works like a signaling game. By jump-bidding, the jumper signals that he has a high value, and so the other bidder should quit immediately if his value is lower. Two bidders, Xenia and Yakov, participate in an auction for a single item. This is a common value auction with the