Abstract: In a building equipped with an outward swinging security door of the type having a double cylinder mortise type key lock mounted in a grille type metal structure characterized by an assembly of interconnected welded rod-like members with spaces therebetween, a means is provided which is immediately available to occupants of the building for locking and unlocking the security door when a corresponding inward swinging prime outer door of the building, spaced away from and rearward of the security door, is opened and is out of view of and inaccessible when the prime door is closed to persons attempting to unlawfully enter the building. The means which is immediately available to occupants for locking and unlocking the security door comprises a rearward opening tubular housing attached to the rearward portion of the security door and a key inside of the housing engaging the rearmost cylinder of the lock.