The online catalog, commercial discovery layers, the open Web, and books available for browsing in libraries all aid in the process of discovery of resources. An absence of books means one fewer discovery method available. It is important, therefore, that libraries retain physical books in open stacks to offer communities a hands-on opportunity to discover and use resources. Applying the same expertise and human insight to decisions about the collections libraries make immediately available on site also affords an opportunity to increase the effectiveness of in-person discovery. This article makes a case for open stacks in the design of libraries.