A bookcase, or bookshelf, is a piece of furniture with horizontal shelves, often in a cabinet, used to store books or other printed materials. Bookcases are used in private homes, public and university libraries, offices and bookstores. Bookcases range from small, low models the height of a table to high models reaching up to ceiling height. Shelves may be fixed or adjustable to different positions in the case. In rooms entirely devoted to the storage of books, such as libraries, they may be permanently fixed to the walls and/or floor.