Misleading opponents

Following position might seem uninteresting:

♥K94 (dummy)

♥QJT2 (declarer)

However, if LHO has the Ace, you may be able to mislead him for an overtrick.

Defending 5♣ (only ♣ were bid) and you already have 1 trick, what would you play if RHO leads ♥J to K94? I think most of us would play small and hope partner has the Q. Now declarer plays the K which obviously holds. Next he starts ruffing a long side suit (which will become high) and plays the ♥2, dummy having 94 left. Will you play the Ace now?

Perhaps it seems hard to see, but when you look at it for a moment you'll notice that there's no real reason not to play the Ace! If partner had Qx, declarer has 5♥s which is almost impossible. So either partner had Qxx (or more) and it doesn't matter, or partner had 3 small and you have to take it now before declarer pitches his ♥ losers on his long sidesuit.