South leads the ♣K, and north follows
East to guarantee a contract of 7♥.
Dummy discards a diamond as east wins the ♣A. A trump is led to dummy and the small spade is ruffed. Another trump lead is followed by a ruff of the ♠Q. Trumps are drawn. East discards the ♦ A-K on the last trump and the ♠A.
Trap: discarding a spade at trick one would leave declarer unable to shorten his trumps sufficiently; he would be at the mercy of opposing red-suit voids. Also, it is possible for the ♠A to be ruffed by south; therefore, it cannot be cashed prematurely.