Fold: the part where the cover of a book is folded in. First, it looks good. Second, the cover is not easy to be damaged. Third, the author's photo and brief introduction are usually printed on it. Folding is a binding form in which the front edge of the cover of a paperback book is about 20 ~ 30 mm wider than the front edge of the book block, and then the cover is folded in along the front edge of the book block.

The back of a book (spine) refers to the part where the front cover and the back cover of a book are connected, which is equivalent to the thickness of the book block. After printing, in order to make the inner core of books and periodicals, the pages are folded in the correct order to form a flat spine edge. After punching, gluing or wire binding, plus the cover, the spine is formed, also known as the spine. Magazines bound on horseback have no spine.

The waist seal, also known as "book waist paper", is a form of attached seal, which is wrapped in the middle of the book cover with paper tape and belongs to external decoration. The waist seal is usually made of strong paper. It is wrapped around the waist of the book cover, and its width is about one-third of the width of the book cover. It is mainly used to decorate the cover or supplement the lack of cover performance. In addition, there are waist seals used for clothing decoration.