A locking screw assembly is provided which allows installation into a plate-like member using relatively little force, but which requires relatively great force for removal. The fastener has an annular locking ring provided within a groove in the head of the screw to allow the screw to sit within or flush with the anterior surface of the plate. The through-hole in the plate which receives the locking screw comprises a ledge and an undercut. When the fastener is installed into the plate, the locking ring resides within the undercut and is prevented from backing out by the ledge. The locking ring has a leading surface that may be chamfered or radiused and a trailing surface that may be flat. The chamfer allows the locking ring to easily be inserted into the through-hole by interacting with the through-hole. After installation, the trailing surface contacts the ledge.