Designed for use on inward opening doors. Incorporating a slam action square hardened steel bolt which automatically deadlocks. A 10 disc Ava mechanism allows for 50,000 key variations to eliminate opening by manipulation or false keys. The outer cylinder and lock case are protected from drill attack by hardened steel plates and pins, whilst the specially designed cylinder will restrict torque attack. As an added security feature the internal knob can be locked which is a particular benefit if fitted to a glazed door.