The Question and Answer section for The Maze Runner is a great resource to ask questions, find answers, and discuss the novel.
What chapter is this referring to?
In the beginning of the story, Thomas is trapped in a large, metal box.
Chuck placed a wooden crate outside of the bathroom and tapped on the window. Gally's response was to open the window and ask who was knocking, which was Chuck's cue to jump and and scream, causing Gally to fall.
"The bathroom," Chuck whispered.