Snapdragon double

A Snapdragon double is a call by fourth hand, when three different suits have been bid. It shows a good holding in the fourth suit (generally six cards, though some partnerships allow five) and tolerance for partner's suit.

For example, after 1Diams 1Hearts 1Spades, a double would show a hand with primary clubs and heart tolerance. The definition of "tolerance" varies among partnerships, and may include any doubleton, only honor doubleton, or require three-card support. A typical hand for most partnerships would be Kxx Kx xx QJTxxx.

In standard bidding, this would be a penalty double, but it is extremely rare to have such a double at the one level, and even there, the opponents may have a better spot. An alternative modern interpretation is for this double to show "cards," and simply ask partner to do something intelligent.

References

[http://www.pitbulls.shawbiz.ca/Support%20Doubles%20-%20Snapdragon.htm Article by Bob Crosby]