safety lock

名词 safety lock:

1. guard consisting of a locking device that prevents a weapon from being fired
   同义词：safety catch
2. a bolt that cannot be moved from outside the door or gate
   同义词：safety bolt

1. I bought another safety lock as an additional insurance against thieves.
   ＂我又买了一把保险锁，以加强防贼的安全措施。＂