Allow for bad splits

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

==

       West   North   East   South
       3♣    4♣     Pass    4♥
       Pass   6♥     All Pass

The 4♣ bid was takeout for the majors. After South took a preference to hearts, North could see no way to intelligently explore, so shot it out with 6♥.

West led the ♣A. Declarer could see that if trumps were 4-0, then he needed spades to divide 3-2. Declarer tested that by drawing one round of trumps with the ♥A. Now what if hearts divided at least 3-1, but the spades were 4-1? Can you see what he had to do?

South cashed one high spade, then led a diamond to his ace. He advanced a spade. West could see that if he ruffed, declarer would have an easy path to 12 tricks.

Suppose West (correctly) discarded. South would win the second round of spades with dummy's king to lead a third round. This should be ruffed with the ♥Q. Notice that if he ruffed with the ♥9 instead, West can overruff and lead a third round of hearts to defeat the contract.

Next, South ruffed a diamond in dummy to lead a fourth round of spades, ruffed with the ♥9. As the cards lie, West can overruff, but to no avail. Declarer can win the return, draw the last trump and the spades in dummy are established. If West refused to overruff, South can ruff a club back to dummy, cash the king of trumps, and run the spades, losing a trick when the trumps were divided 3-1 originally.

Here's the same deal presented with the BBO Handviewer:



You can click on "next" and Handviewer will show you the first trick. Click "next" again to see the second trick, etc.