nail up a door的意思|示意

That which you see there, higher up in the door, near a nail, is the hole of a big iron bullet as large as an egg.

稍高一点，在这大门的上面，那颗钉子旁边，您看见的是一个大铳打的窟窿。

Pin a nail on the outside of the door frame and leave a part of protrusion. Making the exposing part of the nail make up the gap between the door and door frame.

在锁舌外侧的门框上钉一枚铁钉，预留部分凸出，并使铁钉露出木头部分的长度正好弥补木门与门框之间的空隙。