Rusinow leads is a bridge convention used as part of defensive carding. Rusinow leads are commonly used only on the opening lead against a suit contract.
In accordance with the convention the second highest honour card is led from touching honours against a suit contract. So from ♥KQ94 a player using the Rusinow Lead convention would lead the Q. This eliminates the ambiguity of the lead of the King against a suit contract where the partner of the leader may not be clear whether his partner has the Ace or the Queen.
They were developed by Sydney Rusinow in the 1930s, but were banned until 1965 by the American Contract Bridge League.