Locking device for keyholes

A security locking device for a keyhole and the like comprised of a base plate, means adapted to secure the plate about the keyhole, an opening in the plate adapted to be aligned with the keyhole, a cover plate, means mounting the cover plate to the base plate to selectively cover and uncover the opening, means locking the cover plate to the base plate, said locking means including aligned openings disposed in each of said plates, a locking cylinder disposed in said opening, said locking cylinder including securing means mounted thereon, means mounting said securing means for movement into and out of the cylinder and actuating means controling said mounting means for moving said securing means.

A cylinder adapted to be disposed in an opening for locking the same therein including a housing, at least one pin disposed therein, means mounting said pin for movement into and out of said housing, said means including a post rotatably disposed in said housing and supporting said pin, actuating means engaging said post for rotating the same, means retaining said actuating means in said cylinder until the same is rotated, and wherein said retention means comprises an L-shaped member having one end anchored in the cylinder and the free end positioned over a portion of the actuating means.