An extra trick in the play

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

South opened 1♥. Because North-South were vulnerable and East-West were not, West felt safe bidding 2NT. North bid 3♣, unusual over unusual. West had shown length in the minors, so bidding either minor would be a cuebid. In the North-South methods, the lower cuebid showed a limit raise or better in the lower unbid suit -- hearts. The favorable vulnerability persuaded East to jump to 5♣.

What would you do with the South hand? South decided to bid 6♥. His thinking was that the opponents bidding and raising the suit he was void in improved his hand. With the information from the 2NT bid, South felt he might gain a trick in the play. He was right.

West led his singleton heart. Notice that the contract makes easily if he leads either minor. South won the lead in dummy and ruffed a club. He led a heart to dummy and ruffed the ♣J. Next, declarer played three rounds of spades, ending in dummy. Finally, he played the ♣K and discarded a diamond.

West was endplayed. A diamond would be a "feeder" into the ♦A Q and a club would provide a ruff and sluff. Either way, he had 12 tricks and his contract. If East had unexpectedly turned up with the ♣A, declarer could ruff and play a low diamond to endplay West.