As declarer, with K J 9 facing A 5 4, you may have reason to suppose that the queen is badly placed for you and again you lead the jack, planning to finesse the nine if it is covered - a "Backward Finesse". (It was a German friend, with excellent but non-colloquial English, who, having executed that manoeuvre, delighted his audience by explaining that he had "touched the queen from behind".)
Justin Hackett won the award for the best play on this deal from the World Junior Championship in Bali. After West had passed as dealer, South ended in Four Spades. West led the king of diamonds, which was allowed to hold, and continued with the queen.
Justin won, led a trump to the jack and ace, and won the trump return. Then he led the jack of clubs (which East did not cover) to his ace and drew the last trump. Up to this point, West, who had passed as dealer, had produced the ace of spades and the king and queen of diamonds. Furthermore, East had shown no interest in covering the jack of clubs. It was long odds, decided Justin, that East held both the ace and jack of hearts.
Backing his judgment, he led the 10 of hearts from dummy and let it run when it was not covered. If East had covered with the jack, of course, he had planned - unless the nine appeared - to finesse dummy's eight on the next round.