Routine processing of library books frequently means using shelves and other spaces as staging areas for incoming and in-process items. As gifts and purchased books are acquired, cataloged and labeled, librarians typically work on them in batches, sorting on to separate shelves those which have not yet been searched in the catalog or which represent additional copies for the collection or which require a certain level of cataloging, etc. As they move through the processing of getting them to the library and ultimately, the reader they are moved from place to place in the back-rooms of library work areas.