What is the common binding method of ancient books in Song Dynasty?

As we all know, China is the birthplace of papermaking and printing. Engraving printed books originated in the Sui, Tang and Five Dynasties and flourished in the Song Dynasty. The binding of woodcut books developed from scroll loading, warp folding, whirlwind loading and butterfly loading to back loading, and thread-bound books appeared after the Song Dynasty. A batch of thread-bound books are also made of cardboard and green cloth paste into "letters" and matched with ivory coins. This binding is easy to read and not easy to break. It is the most advanced traditional book binding technology in China and has been popular in Ye Genyou for hundreds of years. "Thread-bound book" has also become another name for ancient books in China. In recent ten years, a large number of thread-bound books have been published. China Bookstore publishes twenty or thirty kinds of thread-bound books every year, and Shanghai Ancient Books Publishing House and Jiangsu Yangzhou Guangling Bookstore also publish many thread-bound books every year. 1993, China thread-bound book bookstore, the first professional publishing house of thread-bound books in China, was established in Beijing. This publishing house has published nearly twenty kinds of thread-bound books.