Abstract: A rotatable lock plug having a key slot formed entirely axially therethrough has a barrier secured in the lock plug adjacent the key slot inner end between an inner end of a key received in the key slot and a torque blade operably connected to the lock plug inner end for providing a barrier denying surreptitious access through the key slot. The barrier has edge portions received in appropriate lock plug recesses and preferably a flat portion transversely spanning the key slot. In one form, the barrier may be an axially slotted pin receiving the key end within the slot, and in other forms may be edge secured, flat plates.

Abstract: A conventional keyed, pin-tumbler lock has an abutment portion formed on the key axially adjacent one of the key notches at the side thereof axially inward of the lock cylinder which normally axially obstructs that lock pin when the key is properly inserted in the lock cylinder key slot to prevent normal withdrawal of the key from the lock cylinder while still permitting free rotation of the lock cylinder by the key in its normal locking and unlocking movements. A key removal member is axially insertable into the key slot adjacent the key within a key axial recess and has a leading angled surface portion terminating axially in a raised surface portion which progressively move and ultimately retain that particular pin from its key pin notch and the key abutment portion obstruction, thereby permitting normal key removal from the lock cylinder.

Abstract: A preferably cylindrical body has a closed bottom bolt opening with an internal spring pressed plunger constantly urged at an angle less than 90.degree. to the bolt opening into interference partially within the bolt opening and retained against such movement by a selectively movable plug within the bolt opening. A bolt preferably having an enlarged head has a recess at an opposite end portion formed generally transversely therein. The bolt end portion is inserted into the body bolt opening displacing the plug further inwardly into the bolt opening and ultimately aligning the bolt end portion recess with the body plunger causing positive interengagement therebetween and permanently preventing withdrawal of the bolt from the body. An annular shoulder of the bolt may engage a body surface at the outer end of the bolt opening during such interengagement to permanently block off the body bolt opening.