Support Doubles in Bridge: Three-Card Support Explained

A support double is opener's double, after partner responds in a suit and the next opponent bids, that shows exactly three-card support for responder's suit. A direct raise shows four. So after 1♦ (P) 1♠ (2♣), opener's double says "I have three spades," and 2♠ says "I have four."

Support doubles are an optional agreement, popular with 2/1 Game Force players and common in tournament bridge. They are not part of the SAYC booklet, so check with your partner before you use them. Acol pairs who play them use the same rules.

The point of the convention is the difference between an eight-card fit (4-4 or 5-3) and a seven-card fit (4-3). Responder may have only four cards in their suit. When opener raises directly, responder knows the side has eight trumps at least. When opener doubles, responder knows the side has seven, or eight if responder has five.

Three conditions:

1. Opener opened one of a suit and responder bid a new suit at the one level, usually a major. Many pairs also include 1♣ (P) 1♦, but the main use is with a major.
2. Responder's left-hand opponent (opener's right) bid: an overcall, a cue bid or a double.
3. The opponent's bid is below two of responder's suit. After 1♦ (P) 1♥, an overcall of 1♠, 2♣ or 2♦ leaves room for opener to double or raise to 2♥. An overcall of 2♠ takes away 2♥, so the double there is not a support double; most pairs play it as takeout or penalty by agreement.

When the opponent doubles instead of bidding, opener redoubles to show three-card support. This is the support redouble.

Once you play support doubles, every other call by opener denies three-card support:

• A raise shows four-card support. The level shows the strength: two-level = minimum, jump = invitational (about 15-17), game = 18+ with four trumps.
• 1NT or 2NT shows a balanced hand, a stopper in the opponent's suit and at most two cards in responder's suit.
• A rebid of opener's suit shows a six-card suit or a hand with nothing better, again with at most two cards in responder's suit.
• A new suit is natural.
• Pass shows a minimum with no clear bid and fewer than three cards in responder's suit. Pass is also correct with a trap hand in the opponent's suit: if responder reopens with a double, opener can pass for penalty.

This rule makes responder's job easy. If opener did not double and did not raise, responder knows there is no eight-card fit unless responder holds five or more.

Responder treats the double like a raise to the two level with three-card support. The minimum strength is the same: opener has 12+, and the double is not forcing beyond that. Responder's options:

• Bid the suit at the cheapest level with five cards and a minimum (6-9). With four cards and a minimum, still bid the suit at the two level: a 4-3 fit at the two level usually plays well enough.
• Jump in the suit with five cards and invitational values (about 10-12).
• Bid game with five cards and 13+, or 4-3 with a strong hand and short in the opponent's suit.
• Bid notrump with four cards in the major and a stopper in the opponent's suit: 2NT invitational, 3NT to play. A 4-3 fit often plays worse than notrump at game level.
• Bid a new suit to look for a better contract, usually forcing.
• Pass with length and strength in the opponent's suit. That turns the support double into a penalty double.
• Cue bid the opponent's suit with a strong hand to ask opener for more.

You are South, the opener. You hold ♠KJ5 ♥A84 ♦AQ763 ♣92, 14 HCP with three spades.

Without support doubles, your rebid is awkward: 2♠ promises four spades, 2♦ promises six diamonds, and 2NT shows more strength and a club stopper, which you do not have. The double shows your hand in one call. Not every system card plays it this way: see what this double means in every system.

North has five spades and 9 HCP, so the 5-3 fit is known. North jumps to 3♠, invitational. You have 14 HCP, two aces and a good five-card side suit: accept. Double dummy, 4♠ makes on this layout: declarer loses only two clubs and the ♠A, and the long diamonds take care of the rest.

Two more hands, same auction 1♦ (P) 1♠ (2♣):

• ♠Q52 ♥K10 ♦AJ764 ♣KQ8: double. Three spades, 15 HCP. You may bid notrump later to show the club stopper and extra values.
• ♠Q5 ♥AJ3 ♦KQ1073 ♣K104: 15 HCP, two spades and a club stopper. A 2NT rebid would promise more strength, so pass. If partner reopens with a double, you pass again and defend 2♣ doubled.

Every convention gives something up. Support doubles cost you:

• The penalty double of the overcall. When you hold ♠KQ109 over a 1♠ overcall, you cannot double for penalty. You pass and hope partner reopens with a double, which partner usually does with shortness in spades.
• Some information to the defense. The opponents learn the exact trump length on the auction. A good declarer uses this too, so it costs little in practice.
• Memory load. Both partners must remember that a raise now shows four. Forgetting it once can cost a game.

Most experts think the gain is worth it, because finding out whether the trump fit is seven or eight cards is more important at the two level than an occasional penalty.

• Raising with three trumps. With support doubles on, a raise shows four. With three, double.
• Doubling with two trumps. The double is not "I have a good hand." With a doubleton in partner's suit, choose another call.
• Responder passing the double with a weak four-card suit. Pass converts the double to penalty. Only pass with a strong holding in the opponent's suit.
• Using it above two of responder's suit. After 1♣ (P) 1♥ (2♠), there is no room for a support double. Agree what the double means there.
• Forgetting the support redouble. After 1♦ (P) 1♠ (X), redouble with three spades.

1x (P) 1M (overcall below 2M) ?

• X: exactly three cards in M, any strength.
• 2M: four cards in M, minimum.
• 3M: four cards in M, invitational.
• 4M: four cards in M, game values.
• 1NT / 2NT: balanced, stopper, fewer than three cards in M.
• Rebid own suit: six cards or nothing better, at most two cards in M.
• New suit: natural, at most two cards in M.
• Pass: minimum with no clear bid, or a trap in the opponent's suit.

1x (P) 1M (X) ?

• XX: exactly three cards in M.
• 2M: four cards in M.
• Other bids: as above, fewer than three cards in M.

Responder after X (or XX): 2M with four or five cards and a minimum; 3M invitational with five; 4M with game values and five; 2NT / 3NT with four cards in M and a stopper; Pass to defend.

Support doubles help most in competitive partscore auctions, which are hard to judge from a book. The BridgeDummy bidding puzzles give you real auctions with interference, and every option is checked over many deals that fit the auction. You see how often the 4-3 fit plays well, and when notrump is better.

To make the agreement automatic, play deals in the Bidding Room with EPBot robots in 2/1 Game Force.

Related pages: negative double, doubles in bridge, opener's rebid and the Law of Total Tricks.