~Support Double

The use of a double of an enemy suit bid to show 3-card support for partner’s suit. Though typically used by opener to show support for partner’s major-suit response at the one level, it may also be used to show support for partner’s overcall suit. The bid is used through an enemy bid of 2H.

Examples:
You Opp Partner Opp
1. 1D P 1H 2C
Dbl
Shows 3-card support for partner’s heart suit and denies any extra values.
2. P 1D 1S 2D
Dbl
Shows the same 3-card support for partner’s suit; The bid is not invitational.

The Support Double shows exactly 3-card support; therefore, a bid of partner’s suit would show 4-card support.

This same approach can be used if the enemy doubles. A redouble shows the three-card support and a bid of partner’s suit shows 4-card support.