The double, a bid that doubles the points or penalty scored in a hand of contract bridge, is a tricky but useful bid. It can give your partner information about your hand, help you reach the optimal contract and put you at a point advantage over your opponent. For beginning bridge players, there are two basic types of double bids: the takeout double, which is a request for your partner to bid, and the penalty double, which seeks to maximize the penalty your opponents receive when you set them on a contract. Once you've mastered these basics, you'll be able to yield and recognize a wide variety of double bids to enhance your bridge bidding strategy.
Determine the the total point value of your hand. Aces are worth four points, kings worth three points, queens worth two points and jacks worth one point. Count points for distribution as well. A void, a suit in which you have no cards, is worth five points. A singleton, a suit in which you have one card, is worth three points. A doubleton, a suit in which you have two cards, is worth one point. In general, do not count face card values in suits in which you have doubletons or singletons. An opening-bid strength hand is any hand with at least 12 points.
Watch your opponent's opening bid. If you have an opening-bid strength hand, you might want to employ a takeout double. You'll do this when your opponent bids a suit in which your hand is weak and you have sufficient support--at least three cards--in the three remaining suits. This forces your partner to bid to give you an idea of the strength of his or her hand without you having to bid and potentially ratchet up the bidding to a contract you cannot complete. Under bidding conventions, your partner must respond unless your opponent's partner interrupts the double with another bid or if your partner has a strong enough hand in the bid suit that he or she thinks the opponents' contract can be stymied.
Even when takeout doubles are not appropriate, use your hand strength and distribution to determine whether a penalty double would be beneficial. A penalty double is a gamble but, when played properly, it can hurt your opponent's score significantly. For instance, bid double if your opponents have reached a game-level contract and you hold a strong hand in their chosen suit. If your partner opened the bidding--indicating a hand of at least 12 points-- and you hold nine or more points, you have a strong enough hand to bid a penalty double on any no trump bid by your opponents. Unlike other double bids, penalty bids do not invite a response by your partner. He or she should respond with a pass.
Study the more advanced doubling strategies outlined in the chart linked in the resources section of this article. Accomplished bridge players can use a double to reveal numerous details about their hand. These include a negative double, which can show strength in a specific suit, or a reopening double, which can prevent your opponents from winning an easy contract. Make sure your partner is well-versed on these strategies, too, and knows how to respond appropriately.