During manufacture, most fibers will line up parallel to each other resulting in a predominant grain direction. Grain direction influences the strength of paper and board and has implications for folding, gluing, etc. The perfect binding machine will saw off this portion of the spine edge of the text block. This ensures that every sheet in the book has a well-prepared edge to receive glue. The top of a book when looking at the front cover, the top of each page.
Headbands also tailbands.
In medieval times, head and tailbands were an integral part of the hand-sewn construction of a book. Head trim The distance between the edge of a sheet or folded signature and the final trim at the head of a book. It is critical that the binder knows the correct head trim, as well as the trim size, to deliver books as they were designed. Hot melt Any of a number of adhesives used in perfect binding machinery. The ridges produced on the spine of a book that has been hand sewn.