Shelf space is a precious commodity in libraries, especially for special collections, which rarely deaccession materials. To deal with this problem, many librarians try to maximize efficiency in their shelving approaches. A common solution to space constraints is adjusting shelves to store materials by size categories. This approach is understudied, however, and projects to reorganize materials by size are often undertaken with little more than anecdotal evidence or intuition to support them. Using a reorganization of the oversize materials at Special Collections at the University of Missouri as a case study, this article lays out some concrete numbers for librarians who are considering shelving their books by size. The study indicates that subdividing oversize materials into upright and flat shelving can result in an increase in shelving efficiency of up to 600 percent for the materials that are stored upright. A systemic approach to shelving by size also offers some preservation benefits, especially for materials that are stored flat.