Abstract: A locking device (1) is provided for a door latch in which a latch bar of the door latch mechanism is turnable to retract a latch bolt of the latch mechanism. A locking means is adapted to be actuated in response to turning of a door handle (3) for the latch mechanism in anti-clockwise direction so as to lock the latch bolt in its extended latching position. It is released by turning the handle in the clockwise direction.

Abstract: A lock mechanism includes a casing structure adapted to be mounted to one of a door and a door frame for cooperation with an apertured strike plate mounted to the other of the door and door frame. The lock mechanism further comprises a front plate for the casing structure with a pair of apertures therein and a latch bolt retractably mounted with respect to the casing structure and biased to an extended first position wherein a latching portion thereof extends from one of the front plate apertures for engagement with the strike plate aperture, and movable to a secnd retracted position. The latching portion of the latch bolt has a beveled leading surface located for engagement with the strike plate only when the latch bolt is moved a predetermined amount toward the retracted position.