Take another look

Suppose you are playing 7♥ on this layout:

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

West leads the ♣Q and you win the ace. Now what?

If trumps split, making the contract is easy. You can draw trumps, run the spade suit and discard the club loser from dummy. Later, you can ruff your club loser in the North hand. That requires only that hearts divide at least 3-1.

Would I give you a deal where it were that easy? Nope, so you better decide what to do if trumps split 4-0. The answer is to reverse the dummy. Ruff two diamonds in your hand. Then, you can score four heart tricks, two diamond ruffs, five spades and two clubs for 13 tricks.

Accordingly, you lead a diamond at trick two and ruff it. Now, when you play the ♥K, East shows out. Don't say I didn't warn you. Here are all four hands:

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

There is one little gotcha, however, that you needed to play for. Remember I said ruff a diamond? Didn't that sound innocent enough? If you ruffed with the ♥4, you will go down because you will have to use a spade to get to dummy to draw the last trump, after you ruffed the second diamond. Yes, there is a spade void. You didn't think I'd post an easy deal, did you? Not happening.

While a singleton club occurs more often than a void in spades, West is highly unlikely to have led a singleton queen against a grand slam. Given that, when West has four trumps, you should plan to use the ♣K to get back to dummy to draw the last trump.

Let's take another look at how the play should go: Win the club lead and ruff a diamond with the ♥9 (instead of the ♥4), cash the ♥K Q, and lead the ♥4 to finesse dummy's 8. Now, do you see the necessity of ruffing with the 9?

After a second diamond ruff (with the ♥J), cross to dummy with a club, draw the last trump, and you have 13 tricks -- you play them so well!

What would happen if it were East who had four trumps? Then you would have to hope East began with at least two clubs and one spade, because you need the two remaining black-suit entries to arrange the second diamond ruff and draw the last trump. That would surely work -- I'm not that mean, am I?