Many doubles populate the bridge landscape: penalty doubles, takeout doubles, negative doubles, maximal doubles, support doubles, free doubles, cooperative doubles, inhibitory doubles, lead-directing doubles, offside doubles, sacrifice doubles, Lightner doubles, Rosenkranz doubles, stripe-tailed ape doubles (seriously), snapdragon doubles (ibid). Here’s one of the least known and appreciated: the responsive double.

When your left-hand opponent opens in a suit, your partner bids another suit and your right-hand opponent raises LHO’s suit, a double shows respectable points and the two unbid suits.

West was dealing, with both sides vulnerable, in an OK Bridge game online:

NORTH
♠A J 9 5 3
♥K 9 4
♦Q 5
♣A 8 4

WEST                  EAST
♠K Q 8 2           ♠10 6 4
♥A 6                  ♥J 10
♦J 8 7                ♦K 4
♣K J 10 9          ♣Q 7 6 5 3 2

SOUTH
♠7
♥Q 8 7 5 3 2
♦A 10 9 6 3 2
♣ —

The bidding proceeded as follows:

West           North           East           South
1♣            1♠               3♣•           DBL••
Pass           3♥               Pass           4♥
All Pass

• Weak
•• Responsive (promising hearts and diamonds)

Opening lead:♣Q

South’s double showed length as well as strength in hearts and diamonds, since North might be short in them. Never mind high-card points when distribution is so extreme: after North bid 3♥, South had no trouble raising to game. No matter how East-West defended, the contract was bound to make. Please note that North-South bid and made the contract with only 20 HCP. That’s how important distribution can be.

Responsive doubles also apply when partner makes a takeout double:

West             North           East           South
1♣               DBL            2♣            DBL•

• Support for all three unbid suits

Or:

West             North            East            South
1♠               DBL             2♠              DBL•

• Pick a minor (with four hearts, South would bid 3 ♥)

You and your partner should decide up to what level of the opponents’ bidding you play the responsive double. I like 4♥.