You searched for: “juxtapositions
juxtaposition (verb), juxtapositions; juxtapositioned; juxtapositioning
An act or instance of setting something close together or next to each other: Jeanette, who loved flower vases, juxtapositioned the various sizes, shapes, and colors on the shelves to show how they compared and contrasted with each other.

June, the librarian, was in the process of juxtapositioning the books so those that were of the same height would be juxtapositioned with one another on the shelves.