Scroll books written on paper, also known as "paper", prevailed from the Southern and Northern Dynasties to the Tang Dynasty. Tens of thousands of ancient books found in the Thousand Buddha Cave in Dunhuang are almost all in the form of scrolls. This paper roll is about a foot wide and varies in length. Draw a column with lead or ink on the roll, which is called Wu Si column; Painted with Zhu, it is called Zhu Sizhu; The upper and lower frames are called columns; The line separating each line is called margin, also known as boundary line or line breaking. Buddhist scriptures generally write 17 words per line, while other ancient books have different words per line. After the paper scroll appeared, China began to use the "roll" as the unit of measurement for books. A book often has several volumes or even dozens or hundreds of volumes. You have to put the word "Yi" on the outside of the scroll. The scroll, outside, is like a book put on clothes, so it is called a "book coat". A book with few volumes contains only one volume, and many volumes are divided into several volumes. Woven with thin bamboo curtain, covered with silk, silk, silk, silk and other silk or hemp, in various colors. After the scroll is wrapped in paper, the title of the scroll needs to be marked, so that it can be found on the bookshelf (Figure 1 [Sketch of scroll check (left) and expansion (right)]). Therefore, a small ivory label, commonly known as "toothpick", is hung on the outer end of the shaft, which is engraved with the title and volume name, and sometimes dyed in different colors to distinguish the four major books: classics, history, volumes and collections.