A bidding box is a box containing cards used in the auction. Its primary purpose is to eliminate unauthorised information passed by words, especially across tables.
A bidding box contains the following:
- 1 card of each of the possible 35 bids,
- about 6 pass cards (green),
- about 4 double cards (red),
- about 2 redouble cards (dark blue),
- 1 of each of alert (light blue), stop (red), and director! (orange) cards.
To make a bid, the intended bid with the pile of lower bids is pulled together and placed on the table facing the partner, but not covering the earlier calls.
To make a pass, double or redouble, the intended card is pulled one at a time and placed on the table facing the partner, but not covering the earlier calls.
To make an alert, the alert card is thrown towards partner's alertable call, and is taken back after RHO makes the subsequent call.
The stop card is used when making a skip bid. Before making the skip bid, the stop card is put in front of LHO. The stop card is taken back after 10 seconds making the bid.
To call the director, one raises the hand holding the director card.