Abstract: A lock assembly comprises a stud for mounting on one member such as a door, a plate for pivotal mounting on another member and a separate locking member for locking the plate to the stud having locking mechanism comprising a cylinder slidable in the locking member and onto the stud, a ball movable through the cylinder wall from a locking position where it engages a groove in the stud and an unlocked position, a ring catch for holding the cylinder and thus the ball in their locked positions and a key-operated lock for operating the catch and also a dead lock.