unloading door造句

This air pressure can also be used to operate loading and unloading doors on passenger coaches, the main reservoir pipe is also used to supply air to operate doors and air suspension.
Within each retort-house, the retort benches would be lined up next to one another in a long row; each retort had a loading and unloading door; affixed to each door was an ascension pipe, to carry off the gas as it was evolved from the coal within.
It's difficult to find unloading door in a sentence. 用unloading door造句挺难的