A Matchpoint Top
A J 3 2
K J 5 4
A K 10 2
A 10 8 6 5
Q 10 9 7
Q 9 4
K Q 10 7 5
6 3 2
J 7 3
K Q 9 7 3
9 8 4
8 6 5
North/South can make nine tricks in notrump, but their best contract is 4 ♠
Say West leads his stiff heart.
North wins, takes the ace of diamonds, diamond finesse, and the diamond king, pitching a club. A diamond ruff, overruffing East if necessary, followed by two top clubs and a club ruff. West remains with only spades, so South leads a heart and West ruffs low leading to this position (assuming East ruffed ahead of you with the ♠ J
at some point:)
West has to let you score two trump tricks, one now, and one when you lead a heart again.
That's on top of three diamonds, two clubs, a heart, and two minor suit ruffs.
If East doesn't ruff the fourth diamond (or third club after pitching on the fourth diamond,) then the end position is:
Again West has to give you two of your three remaining trumps.