They put the key in the door and entered.
他们用钥匙打开门进去了。
I looked everywhere for my keys and they were in the door all the time.
我到处找钥匙,没想到钥匙一直插在门上。
They had put a padlock on the door of his flat.
他们已经在他的公寓门上上了把挂锁。
There was an old rusting bolt on the door.
门上有一个生锈的旧门闩。
in the:in表地点时,指在某一立体空间范围内,in表示在某范围之内,是其中的一部分。
on the:on表地点时,指某物与另一物表面相接触,或与某地方接壤等,on表示在某范围之外,两者之间一般互相连接。