The Squeeze-Trim-Endplay: Hand
This hand was reported by Don Kersey, in a 1990 article in Bridge World analyzing this type of play, which he called a one-threat squeeze.
The contract was 6NT. West opened first seat with a bid of 3 The opening lead was the J.
As you can see, there are 11 tricks off the top, and just a 4-1 heart break will give you your twelfth. So you might as well plan for the 5-0 heart break, because it's coming.
The main problem with a squeeze-trim-endplay is placing the honors, to know that it is needed, and knowing the distribution, so you can decide whether to attack the suit or endplay in the suit. When Lefty shows out on the first round of hearts, your problems are solved. Righty can't have two diamonds. So you just run your spades and your ace of diamonds, coming down to:
in dummy. If Righty has at any time pitched a heart, you just lose a heart to set up your long heart. If Righty has not pitched a heart, Righty's is holding four hearts and two clubs. Trim the clubs and run the endplay in hearts.
If you tried to run the squeeze-trim-endplay in diamonds against Lefty, that worked too. If there is any chance that Lefty has 6 diamonds, then it is not as assured. The endplay itself doesn't work if Lefty has the J or 10 of diamonds. Also, if you are playing Lefty for seven diamonds and Lefty only has six, you might misguess the ending position (if Lefty comes down to two diamonds and an extra club. Of course, if Righty has a diamond, Righty will probably pitch it -- Righty is, after all, being squeezed in clubs and hearts. A diamond pitch from Righty will give the show away.