Abstract: A plug lock assembly is provided. The assembly comprises a sleeve member to which a detent catch member, a cylinder member, and a latch member are coupled. The detent catch member engages a face wall portion of the sleeve member through cooperating cambered surfaces such that the detent catch member may be placed into and out of its locking position. The detent catch member has formed thereon an open cambered groove section which is engaged by a locating pin extending from the sleeve member for limiting the axial displacement of the detent catch member in at least one direction. This reinforces the lock assembly against compromise of its locking function.