Lock assembly

A hook-bolt lock assembly is improved in strength by hook-bolt plates (5, 6) and can be locked without inserting a key into a lock unit (22) when the assembly is locked, so as to be improved in operability. In the assembly: a movable plate (2) is biased by a spring (3) toward its projecting direction; the hook-bolt plates (5, 6) are pivoted to a casing (1); oblique cam surfaces (16, 17) of front-end hooks (9, 10), which abut on socket members (14, 15) of a stationary frame (13) when a door (12) is closed, are oriented outward in arrangement; a leaf spring (18) interposed between the plates biases them (5, 6) swingably outward; the movable plate (2) has cam projections (19, 20) abutting on outer edges (5a, 6a) of the plates. A rear end of a rotor (23) of the lock unit (22) fixed to the casing (1) is fixed to a base end of an operating-arm plate (24); and a front-end driving projection (25) of the plate (24) is inserted in a slot (26) of the movable plate (2).