Abstract: In a restraining device for releasably securing a person's wrists or legs in which a pair of manacles are made of flexible loops or straps with ratchet teeth at one end of each strap and a lock housing at the opposite end of each strap, each housing is characterized by being of hollow generally triangular configuration with a channel for extension of the free end of each strap through the housing beneath a pawl arm in the housing which is controlled by a specially designed key. The key is guided into engagement with the pawl arm by an extension wall on a cover plate which is permanently attached to the outer side walls of the housing by a combination of notched ends on the cover plate and ultrasonic molding together of the cover plate with the outer side walls and an inner support wall in the housing.