Meanwhile Phil has fallen to work at his usual table, where he screws and unscrews, and cleans, and files, and whistles into small apertures, and blackens himself more and more, and seems to do and undo everything that can be done and undone about a gun.
There are no more uses of "aperture" in the book.
Show samples from other sources
The higher the f-stop, the more closed the camera’s aperture.
It wandered along the crest of the hill and terminated before a fragment of wall pierced by a rough aperture which had once been a door.