Its distinguishing motive is presence of a "vice" menace in one suit, where one defender holds cards of equivalent rank which split the declarer's pair of cards in front of him, where his partner has a winner in the suit.
It was first attested by Terence Reese in the book "The Expert Game", a.k.a.
In other words, the defenders have a "high" finesse position, equivalent to the one in diagram: If West can be forced to abandon QJ, the defenders will take only one trick in the suit.A similar motive is encountered in guard squeezes, however, in the vice, the defenders have a winner in the suit.
NW ES Hearts are the "vice suit", and the second menace is the declarer's ♦8.
When South leads the high ♠5, West must not discard the ♦10; when he parts with a heart honor, declarer leads the heart and East must cede the last trick to dummy's heart ten.NW ES When the second menace (diamonds) is in dummy, it must be a two-card menace accompanied by an entry, otherwise West can safely abandon the suit; if the ♦K were absent, the West can discard the diamond winner, as the declarer will not have the entry to enjoy it.