The trunk with blank or thin lines is called "white mouth", and the thick line or completely black line is called "black mouth". Some fish tails are only on it, and some are up and down. This format has been popular in China for thousands of years.
Sometimes there is a small square outside the sidebar on both sides of the border, which is called "book ear" or "ear son" or "ear lattice", which is called "ear" for short. Endorsement of names on the ears of books is a small problem, which is equivalent to the "middle seam" of modern lead-printed books and the "book eyebrows" of horizontal printed books. Its left part is called "left ear problem" and its right part is called "right ear problem". This is to facilitate reading and searching.
(engraver's) burin