lock and key

例句：

1. 1.She locked the door securely with a big padlock.
   她用一个大锁把门锁得严严实实的。
2. 2.The thief had to break into the house with a lock and key.
   这个小偷不得不用锁和钥匙来破窗而入。
3. 3.The old man kept his keys in his pocket, so he could easily find them if he needed to lock and unlock the door.
   这位老人把钥匙放在口袋里，这样他如果需要锁门或开门时就能轻松找到。