The idea of binding line should not be isolated, because even a paperback book should be regarded as a hexagonal cube as long as it reaches a certain thickness, so the cover, spine and back cover should be regarded as an organic unity in design. Reasonable design according to different processes and accurate calculation of specifications and dimensions. So it is accurate to10 mm.

First of all, paperback books generally have only the cover, spine and back cover, and paperback and hardcover books also have tight mouths. The cover size of hardcover books is often 3mm larger than that of paperback and hardcover books at the top, bottom and front because of indentation and floating mouth, and the spine of books is also increased because of the thickness of cardboard. For example, the cover size of 16 paperback is 18.5× 26cm, and the cover size of hardcover is 18.8× 26.6cm. In addition, when the background color of the cover is different from that of the closed book, the background color of the cover and the back cover should be 3 to 5mm in the closed book direction, so as to avoid exposing the true colors of the front face due to the small spine design. In addition, the spine thickness must be strictly calculated according to different papers, and the formula is: spine thickness is equal to the total number of pages multiplied by the paper thickness plus the cover (or cover) paper thickness multiplied by 2.