Abstract: A lock mechanism particularly for doors having a narrow stile, wherein a unique arrangement of components provides greater security and facilitates manufacture and installation, as characterized by a heavy pivotally swingable main bolt connected at its inner end to one end of a rocker actuating lever, the end of the lever being provided with a unique escapement for the release and control of the movement of the rocker arm by an associated manually rotatable key-actuated cam extension, to move the main bolt between locked and unlocked positions. An important feature of the escapement resides in a unique arrangement of parts which is not critical as to the dimensions of the actuating cam extension, and which readily accommodate to actuating cams that may vary materially in their dimensions. The escapement also enables a better and more symmetrical resolution of the operating forces and the obtainment of maximum security.