Effectively prevents unauthorized removal, even drilling out, of transom bolts on permanently mounted outboards. Heavy-duty locking plate installs under engine transom nut and fits up to 1/2" engine bolts. Polished 316 stainless steel lock assembly completely conceals transom bolt head, protecting it from tampering. Noise dampeners reduce rattle. Includes two keys, which cannot be duplicated without 5 digit key card (also included).