South dealer. Both sides vulnerable.
Contract: 6 by South
Let’s suppose you’re in a contract the outcome of which appears to depend on a finesse. Whenever you run into such a case, you should make it a special point to also look for a way of increasing your chances beyond the 50% probability of winning the finesse.
Take this hand where it would seem that declarer must win the spade finesse to make the slam. However, there is actually a good chance of making the hand even though West has the king of spades, and it costs declarer nothing to that this possibility before attempting the finesse.
Accordingly, he wins the club lead with the ace and cashes the K-Q of hearts and A-K of diamonds. He notes that West plays the 10-8 of diamonds as the suit is led. Declarer crosses to dummy’s king of clubs and plays the five of diamonds.
East cannot afford to step up with the queen, which would crash West’s jack, so he follows low. South does not bother to ruff the diamond because there is an excellent chance that West started with either the J-10-8 or Q-10-8. He discards a spade instead. As the cards happen to lie, West is forced to win with the jack and South automatically has the rest of the tricks because West is endplayed.
The suggested method of play succeeds because the diamonds are favorably divided, but it should be noted that, if they were not, declarer would still have the spade finesse available. The important point is that South substantially increases his chances of making the slam by first sounding out the diamonds.