In the design and administration of any library, a key decision is whether its stacks will be open or closed. In an open-stack library, patrons are free to enter the stacks to browse the collection and retrieve items that interest them. In a closed-stack library, only library staff are allowed in the stacks; patrons must use the catalog to identify books they want, and request that staff retrieve them. Until the late 19th century, most public libraries had closed-stack systems, but toward the end of that century open stacks increased in popularity.
