The Chubb 4L67E British Standard (BS3621) Rim Auto Deadlocking Nightlatch is a high security nightlatch that has a 20mm hardened steel deadbolt and is now branded under Union. The 4L67automatically locks when the door closes providing extra security. The Chubb 4L67E British Standard (BS3621) Rim Auto Deadlocking Nightlatch features include drill, saw, pick and torque resistance and has an internal lockable handle. The Chubb 4L67E British Standard (BS3621) Rim Auto Deadlocking Nightlatch is ideal for glazed doors, as the lockable handle cannot be operated through a smashed window. The Chubb 4L67E is recomended by insurance companys Themechanism uses a 10 disk AVA. Outer cylinder.