Security chain lock

A stop lock unit for securing the chain tab of a chain lock mechanism in place in the slotted lock plate of a conventional door chain lock mechanism, so as to prevent opening of the door chain lock mechanism, comprising

• A conventional door chain lock mechanism with a lock plate that may be fastened to a door, said lock plate formed with a slot, one end of which is enlarged, and a chain that may be fastened to a door jamb, with the free end of the chain fastened to a tab member that may be inserted into the enlarged end of the slot of the lock plate and slid along the length of the slot,
• a stop lock unit adaptable for mounting in the said slot so as to prevent the tab member inserted in the slot from sliding past the installed stop lock unit,
• said stop lock unit being in the form of a pair of shaped plates joined by a reduced neck section and fitted with a through hole, together with a screw which loosely fits in said hole and is adaptable for engaging a threaded hole in the supporting member to which the lock plate is fastened behind the slot of the lock plate, when the stop lock unit is initially inserted into the enlarged end of the slot of the lock plate and then slid in the slot past the enlarged end, in which the neck of the stop lock unit is of lesser width than the width of the slot in the lock plate so as to ride freely in the slot, with the tail plate of the stop lock unit being of greater width than the width of the slot of the lock plate but of a size to fit through the enlarged end portion of the slot of the lock plate.