What is the difference between a ‘shelf’ and a ‘bookshelf? According to the Spanish Royal Academy a shelf “is a unit comprising shelves or levels” and a bookshelf in a “unit with shelves for placing books”;

so the difference lies in the use. If you use them to keep books, your BrickBox will be bookshelves; if you keep vinyl records, films, CD’s, DVD’s or any other thing, they become shelves.