key cap

例句：

1. 1. The key cap on the door is broken, so I can't open it.
   门上的钥匙盖坏了，所以我打不开。
2. 2. The lock cover is designed to protect the mechanism inside the lock.
   锁芯盖是为了保护锁内部的机制而设计的。
3. 3. The key cap was missing from the box, so we had to buy a new one.
   盒子里的钥匙盖不见了，所以我们不得不买一个新的。