There are certain library departments which do not fit the usual distinctions between libraries and archives.
Libraries will often keep rare books in strong rooms and provide access to them only in reading rooms, although rare books are not normally considered archival. These books often include first editions, books which were once collected by famous people or medieval texts written by hand, with wonderful ‘illuminations’ (pictures, often found at the start of a section or in a margin).
Special collections departments often keep rare books and personal papers (the archives of famous or locally important people). Special collections departments within university libraries often keep thesis written by the alumni of that university. Access to materials kept in special collections is often similar to that provided in archives, and they can be managed by librarians as well as archivists.
Many libraries have a section relating to the history and geography of their local region. These combine published and unpublished materials. They may contain archival material but more commonly the items they hold are surrogates (copies of documents). Surrogates are sometimes used to provide access to the information on fragile or frequently-used archival documents, while ensuring the original documents are not damaged through excessive handling.