Bookmarks have been a common library handout for more than a century. They have been used by libraries to accomplish a variety of purposes. Protection of books has been a primary purpose. Providing bookmarks theoretically avoids having patrons turn down the corners of pages. They also discourage patrons from using other objects as bookmarks. Early bookmarks intended for use by children often included guidance on the care of books. Another purpose of bookmarks was to convey the rules of the library. They were used by some libraries as date due reminders. An ongoing purpose has been promoting reading. National Library Week promotional materials always include bookmarks. Summer library programs routinely include bookmarks as one of the freebies. Because of the wide variety of library and other bookmarks, they are a natural collectible. I'm not a serious collector of library bookmarks but I have managed to accumulate a card catalog drawer full of them. I've put images of some of them on a Library Bookmark web page at the Library History Buff website. A nice collection of links on bookmarks is located here.