Reading Eagle – 11 Ago 1992
It’s easy to falsecard by playing a card declarer already knows you hold; it’s harder to play a card when its location is not yet known (but soon will be ).
Lead: 
J
East won the first heart with the A and returned a club. West took the ace and led another club to dummy’s 
J. South next led a trump and finessed with the 
10 (his best play) when East followed with the 9. South then led a second trump to force out East’s ace, won the next club, drew trumps, and claimed his game.
Finesse wins
The bidding indicates that South has only five spades. If West holds the 10. East’s play is moot: but if South has K-10-x-x-x, he’ll finesse with the 10.
Since East knows the finesse will win, he must play the jack. The card he’ll soon be known to hold on the first trump. South wins with the king, but he’s likely to finesse with dummy’s 8 next to avoid losing two tricks if West holds A-9-5-3. East then gets the 9 and ace of trumps to defeat the contract.