Since such collections often hold a large amount of material thatcan be described or referred to in various ways, scholars designate a givenitem with a shelf mark or a call number. An item is usually placed with otheritems in a folder, a volume, or a box, and its shelf mark will identify thelibrary, the collection, the folder (or volume, box, etc.), and the number ofthe item within the folder.4

Up to 1200 the contents list of a monastic library was usually merely an inventory: it marked the presence of a book, but not its location. The later Middle Ages saw a surge of real catalogues, listing books and their location. Some of these catalogues were written out in books (as we will see in a moment), while others were pasted to the wall in the library.