Support Double and RedoublesSUPPORT DOUBLE. A method invented by Eric Rodwell that enables the openingbidder to clarify more precisely the degree of support for partner’s suit in acompetitive auction. If partner responds to an opening bid in a suit and the next player overcalls or doubles, the support double comes into play as long as the overcall does not raise the level above two of responder’s suit. If opener raises responder’s suit, he is showing at least four-card support. If he doubles or redoubles, he is showing precisely three-card support for partner’s major. When opener passes, rebids his suit or bids another suit at his second turn, the implication is strong that (1) he does not have three or more cards in partner’s suit, or (2) he will show support later. Partnerships using support doubles lose the option of doubling the opponent’s overcall for penalty. Examples of the support double: (a)     1♣    1♥    1♠    2♥            Dbl (b)     1♣    Pass    1♥    2♦            Dbl (c)     1♣    Pass    1♥    Dbl            Redbl (d)     1♣    Pass    1♥    2♦            2♥ (e)     1♣    Pass    1♥    Dbl            2♥ (f)      1♦    Pass    1♥    1♠            2♣ (g)     1♦    Pass    1♥    1♠            Pass (h)     1♥    Pass    1♠    2♣            2♥ Opener’s double is showing precisely three-card support for partner’s suit in the first three examples by using the support double or redouble. In (d) and (e), by raising he is guaranteeing at least four-card support for partner’s suit. In (f), (g) and (h), the primary message is that opener has fewer than three cards in partner’s suit because he has (f) bid a new suit, (g) passed and (h) rebid his suit. The support double can be used even when the overcall is in notrump.     1♣    Pass    1♠    1NT     Dbl The double can be for penalty by agreement, but it probably is better to play it as a support double because there are few times when opener can double for penalty in such a sequence. Even playing support doubles, many players use the double for a different purpose in this sequence:     1♣    Pass    1♦    1♠     Dbl By agreement, this double can be used to show four hearts even if the partnership is playing support doubles. Equally, had the bid over 1♦ been 1♥ instead of 1♠, a double could be used to show four spades in a balanced hand, allowing for the agreement that a bid of 1♠ guarantees at least five clubs together with four spades.SOURCE: "Conventions", The Official ACBL Encyclopedia of Bridge, 7th ed. Horn Lake: American Contract Bridge League, Inc., 2011, page 322. Print