Abstract: A portable auxiliary locking device for securing an inwardly opening door of a room or building against unauthorized entry is disclosed. The locking device includes a threaded rod which terminates in an axially extending plate region having a hook-like flange formed at the distal end thereof. The threaded rod passes coaxially through a central opening within a tubular body member having an end face that is configured for abutment with the inner surface of the door. A locking barrel, rotatably interconnected with the second end of the body member, includes a quick-release latch that is spring-loaded into engagement with the threaded rod. In operation, the door is closed with the hook-like flange extending into the opening within the strike plate of the door frame and the threaded rod extending inwardly into the room that is to be secured. The quick-release latch is then depressed and the body member slid into abutment with the surface of the door.