A lock includes a body, a wheel, an outside spindle, and a locking plug. The outside spindle includes a front end having an extension not in contact with a circumferential wall defining a through-hole of the wheel. When the locking plug is in an unblocking position allowing retraction operation of a latch bolt, the front end of the outside spindle is engaged with the wheel to allow joint rotation of the outside spindle and the wheel. When the locking plug is moved from the unblocking position to the blocking position not allowing retraction operation of the latch bolt, movement of a push member pushes the front end of the outside spindle away from the through-hole of the wheel such that the front end of the outside spindle is disengaged from the circumferential wall of the through-hole of the wheel, thereby disengaging the outside spindle from the wheel.