How does Susanna Kaysen use imagery in Girl, Interrupted?

Imagery:

The seclusion room was the size of the average suburban bathroom. Its only window was the chicken-wire-enforced one in the door that allowed people to look in and see what you were up to. You couldn't get up to much in there. The only thing in it was a bare mattress on the green linoleum floor. The walls were chipped, as though somebody had been at them with fingernails or teeth. The seclusion room was supposed to be soundproof. It wasn't.

A nurse would look through the chicken wire and decide if you were ready to come out. Somewhat like looking at a cake through the glass of the oven door.