"Cyclone leaf" is the first step from paper to leaf, and it can also be said to be a transitional form from paper to leaf. Turn wherever you turn, which is extremely convenient to find. Even if you turn it over from beginning to end, the speed is extremely fast, as fast as a whirlwind, so you give it the name "whirlwind leaf". The whirlwind leaves further evolved into a "butterfly suit". Up to now, butterfly bound books are not printed on rectangular boards, but printed on rectangular boards, becoming a number of single-page bound books. The space occupied by a printing plate on paper is called "layout". Blank paper outside the layout is called "up", "down", "left" and "right". The periphery of the layout is called "border", and the thick lines that make up the border are called "sidebar" or "column line". The upper column is called "upper column", the lower column is called "lower column" and the left and right columns are called "left and right columns". The sidebar with only one line is called "single side" or "single column", and a thin line inside the thick line is called "double side" or "double column". There are three forms of "unilateral winding", "bilateral winding" and "bilateral winding", and there is absolutely no one of up and down and unilateral winding. The layout is divided into several "lines" by straight lines. The middle line of the page is called "page center" or "middle seam", and no words (and of course no small notes) are engraved. The center of the board is often divided into three sections by patterns or horizontal lines, and the patterns are called "fishtails" according to their shapes. There is only one fishtail on it, and those with horizontal lines below are called "single fishtail" and some are called "double fishtail".
Butterflies have a disadvantage because the back of the second half of the page is not connected with the back of the first half of the second page, so it is inconvenient to turn over two pages after reading it. Usually, when you open a book, you will often encounter a blank back. So, someone folded back the reverse side of the page (like the later thread-bound book) and stuck the two outer edges of the page on the back of the book, which became "northern packing", also called "back packing".
The present thread was installed in the middle of Ming Dynasty. It appears because Bao Beizhuang is easily damaged at the back of the book. If it is damaged, the brain part of the book will be uneven after two or three times of paper twisting, and the upper right corner and lower right corner of the book will be rolled up very unsightly. Therefore, it was improved on the basis of Bao Beizhuang, that is, after the paper was punched and twisted, instead of the whole book cover, two and a half page covers were used to separate the front and back of the book, and then the brain of the book was punched and threaded, so it was called thread binding. There are certain specifications for line binding. Generally, only four holes are punched, which is called "four-needle eye binding". Sometimes a hole is punched in the upper and lower corners of a thick book, which is called "six-stitch binding". In the Ming Dynasty, book coats were mostly blue (also known as magnetic cyan) and brown (also known as antique and antique). In the Qing Dynasty, they were a little brown, and some of them were mixed with gold, but in the late Qing Dynasty and the Republic of China, they liked to use blue. Most of them are made of two or three layers of paper, and some are made of silk or silk. Set at least one blank sheet of paper, sometimes as many as two or three sheets, between the front cover and the back cover and the text, which is called "page protection" or "secondary page", and some people call it "page reading".
In the Ming and Qing Dynasties, I like to make a book cover for thread-bound books, which is also called "letter" in elegance and vulgarity. Use hard paper inside, blue cloth outside and white paper inside. Wrap the four sides of the book with two toothpicks, leaving only the head and root of the book empty. Exquisite brocade is used instead of blue cloth, and sometimes the head and root of the book are wrapped up, which is called "four in one set" In a four-in-one set, the heads and roots of books are inlaid with moire patterns, which is called a "cloud set". However, because these book covers are equipped with paddles, they are easy to be bitten by rats and easily broken in the outside world, so many people like to use so-called "splints". This is to use two boards the size of a book, and put a cloth belt at the upper and lower ends to fasten the book. Wood boards should be strong, such as catalpa, nanmu, rosewood, jujube, camphor and so on. In addition, some rare cultural relics are often packed in exquisite wooden cases or small wooden boxes, in which the title, edition, album number, collector's name, number or social morality are engraved.