Abstract: A cylindrical lock assembly for mounting in a door panel having a transverse bore includes a lock chassis adapted to fit within the bore which has lever handles on rotatable spindles for actuating a latch bolt. The chassis additionally has a support opening on at least the first side of the door panel. A support plate having a diameter greater than the bore is mounted on each side of the door panel and is non-rotatably secured to the panel. The support plate includes an opening corresponding to and aligned with the chassis support opening. A threaded support plate fastener having a hollow, elongated body with an internal opening extending along its length is adapted to extend through the opening in one of the support plates and into the chassis support opening to non-rotatably secure the chassis to the support plate.