Abstract: A locking key, designed to preserve an indication of the lock-shifting (opening or closing) operation last performed, has a shank with an extension shaft rotatably received in an adjoining head, the relative rotation of the shank and the head being limited to 90.degree. or 180.degree. by a retaining pin in the head coacting with a part-circular recess on the shaft. The pin and the recess also serve to hold the head in a fixed axial position with reference to the shank. A spring-loaded detent in the shaft or elsewhere inside the head serves to index the two key portions in either of their limiting relative positions.

Abstract: A locking key, designed to retain an indication of the lock-shifting (opening or closing) operation last performed, has a head and a shank interconnected by a screw coupling with limited axial play enabling their relative rotation through 90.degree. or 180.degree.. The shank and its bit can thus be positively entrained for a lock-opening or a lock-closing motion only after the head has arrived in one or the other limiting angular position relative thereto. When the idle rotation of the head is 180.degree., the relative angular position of the two parts can be indicated by special markings thereon.