A bone plate (1220) having at least one screw hole (1226a, 1228a) adapted to receive a bone screw (34), a blocker (1280) having a blocking end for blocking a bone screw (34) from further backout of bone the blocker (1280) being predisposed in a blocking position wherein the blocking end at least partially overlaps a portion of the screw hole (1226a, 1228a), the blocker (1280) being moveable from the blocking position by contact with the bone screw (34) during insertion of the bone screw (34) into the screw hole (1226a, 1228a), and a blocker fixation element (1266) having an open orientation at which the blocker (1280) can move from the blocking position and a closed orientation preventing substantial movement of the blocker (1280) from the blocking position. The blocker fixation element (1266) cannot be moved to the closed orientation unless the screw head passes the blocker (1280), thereby revealing that the blocker fixation element (1266) is in position to prevent substantial movement of the blocker (1280).
