? Push lock for bypass sliding doors. ? Back-surface mount lock, counterplate is mounted on the front face of the back door. ? Locking: Turn key 90? to the right, push in, turn key 90? to the left, and remove. ? Unlocking: Turn key 90? to the right and lock will automatically disengage and turn the key 90? back,and remove. ? High-security Million Lock dimple key; one million key changes available. ? Please specify keyed alike or differently when ordering. (2,520 key changes per master key.) ? Master key system available by special order at a surcharge.