You are in a four spade contract, (West and East passed throughout), and the two suits of interest are spades, and a side suit (call it hearts). These are the North and South hands, as given in a bridge column.
S AQJ H A65 D Q64 C QJ74
S T9876 H K3 D 32 C AK32
The opening lead (7 of hearts,covered by East's 9) goes to your K of hearts. You lead a low spade to the Q in dummy for a finesse, and it holds (West and East play 3 and 2). If you now play A and J of spades, you will probably lose a spade to the king, but make your contract, because your natural losers are one spade and two diamonds. On the other hand, you can repeat the finesse by cashing the A of hearts and coming to your hand with a heart ruff. Your fear is that East will ruff with the K, and then go to West via a high diamond for a ruff. In rubber, the right thing to do is to draw opposing trumps as fast as possible by playing A, then "low" (J), in spades, conceding a trick to the opposing king.
But suppose this is Matchpoints (duplicate). Given East's and West's silence, is it reasonable to assume that hearts are split 4-4 or 5-3, and that you can return safely to your hand for a second finesse? If we can earn an overtrick half the time by finessing spades again, will that "make up" for the few times that East can ruff and defeat the contract?
(The column reported that the actual declarer went to his king of clubs, the second spade finesse lost to East's king, and East reached a high diamond honor in West for a club ruff, down one, since clubs were 4-1. This, to me, is a greater risk than the heart ruff.)
The bidding was North (opener) 1NT, South 2 clubs North 2 diamonds South 4 spades. Neither side vulnerable.