A bone plate assembly includes a bone plate and a rotatable lock. The bone plate includes a superior surface, an inferior surface, and at least one screw through-hole that is configured to receive a bone screw. The bone plate includes a locking cavity that defined in the superior surface. The locking cavity includes a bottom surface that is recessed relative to the superior surface, and also includes a post that extends upwards from the bottom surface. The rotatable lock is supported on the post such that the rotatable lock is at least partially within the locking cavity.