名詞 safety lock:

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

1. I bought another safety lock as an additional insurance against thieves.
   ＂我又買了一把保險鎖，以加強防賊的安全措施。＂