Abstract: A dual function lock mechanism includes a body (30,32), and a cam member (34) mounted on the body for rotation about an axis. A retractor (36) is adapted to drive a latch bolt and is supported for sliding movement transversely with respect to the axis. Means is provided to slide the retractor in a first direction to retract the latch bolt from a latch position to a release position. By virtue of respective cooperable mutually engageable formations (41,72) on the cam member and on the retractor means, a predetermined first rotational movement of the cam member is effective to slide the retractor in a direction opposite the said first direction to move the latch bolt from the latch position to an extended lock position, and a predetermined opposite rotational movement is effective to return the latch bolt from the lock position to the latch position. Detent means (64) is provided to engage and thereby normally prevent the retractor from moving the latch bolt from the lock position to the latch position.