A Squeeze-Trim-Endplay (Book Hand)
This is from Adventures in Card Play, by Ottlik and Kelsey. The opening lead is revised.
The contract is 6NT, and the opening lead is a club. This hand is a cute sure-trick problem -- how do you make 6NT against any distribution (and an opening heart lead)? But I will treat it as a hand from play.
Obviously, if spades are not 4-0, the hand is simple. If Righty has 4 spades, you can finesse for the 10. So don't play the king of spades on the first spade trick.
What if Lefty has 4 spades? At my club, you can't think for 5 minutes about a hand then claim when the opponents follow to the first round of a suit. But you can think a little on the hand.
Let's suppose, for the moment, that you lead a spade to the queen. Righty does show out. Now you can think a few minutes on the hand.
Obviously, you can knock out the ace of spades and take the diamond finesse. Alternatively, you can knock out the ace of spades and run a spade-diamond simple squeeze. You can cash all of your hearts and do not have to commit yourself until your discard on the fourth round of clubs.
But there is another way to play the hand. Suppose you cash all of the hearts and all of the clubs, coming down to this situation:
Again, Lefty has to save 3 spades. If Lefty has pitched a heart to save one heart and one diamond, you simply trim them. If Lefty has saved two hearts, the lead of the ace of diamonds
If Lefty comes down to 3 spades and a diamond, you can cash the ace of diamonds, then lead the king of spades to endplay Lefty. (If Lefty ducks, you then simply lead towards the queen of spades.) If Lefty discards a spade to save two diamonds, you can simply knock out the ace of spades. There is no difficulty on your part reading how many spades Lefty has remaining.
Therefore, this is the superior way to play the hand. If you win the first trick on dummy and lead the queen of spades, you destroy this position (because Lefty can win the ace, eliminating any endplay to make the contract). So it would be very nice if you could see this position at trick one. Lacking that, if you happened to play the spades by leading towards the queen, it would be nice if you could see this position when you discover the 4-0 spade break.
How do you see this position? You have to realize the endplay potential in spades. So you see that you could make if everyone (but Righty) had three spades at the end. Obviously, Lefty cannot pitch a spade. So you need to start thinking squeeze-trim-endplay. The loser count, 2, is right. On this hand, diamonds is the obvious suit to hold at the end, because 4 rounds of clubs and hearts will probably eliminate those suits from Lefty's hand. And of course the fact that you don't have to guess at Lefty's final holding makes this an almost sure way to play the hand.
So you start in on hearts. What if Lefty has 5 hearts? You will know after playing two rounds of hearts. Now you want to cash your clubs and end up with this position.
Again, Lefty has to save 3 spades. If Lefty has pitched a heart to save one heart and one diamond, you simply trim them. If Lefty has saved two hearts, the lead of the ace of diamonds squeezes out a heart. (And if Lefty has saved two diamonds, the lead of the heart squeezes out the diamond.)
Alas, if Lefty has clubs, you do not discover this until your entries to the dummy are gone -- you do not have the entries to cash both hearts and diamonds yet end up on dummy at trick 10 where you can lead your good club. If you count out the hand you will see how to play it when Lefty saves 5 clubs.
In the book problem, the opening lead is a heart. Your natural tendency might be to win on the board and lead the queen of spades. That ruins the squeeze-trim-endplay (if Lefty wins with the ace). So you need to see the squeeze-trim-endplay at trick 1 with a heart lead.