Abstract: A belt lock for a belt strap safety system comprising a lock case incorporating a detent mechanism, a lock tongue insertible into the lock case and engageable with the detent mechanism, one or two shoulder strap end pieces each having a carrier element for a shoulder strap to be fastened thereto and a crotch strap end piece for attachment to a crotch strap. Each of the end pieces has an attachment element for retention on the lock tongue and the attachment elements have complimentarily shaped free ends by which the shoulder and crotch strap end pieces can engage and fit together independently of the lock tongue. The lock is assembled by fitting together the attachment elements and then passing the lock tongue through the assembled elements and into the lock case.