A binder was used to cut wheat and bundle it. It would then be picked up and run through a trashing machine.
The graph displays the other subjects mentioned on the same pages as the subject “binder”. If the same subject occurs on a page with “binder” more than once, it appears closer to “binder” on the graph, and is colored in a darker shade. The closer a subject is to the center, the more "related" the subjects are.