Woodblock printing
Woodblock printing also changed the shape and structure of books. Scrolls were gradually replaced by concertina binding (經摺裝) from the Tang period onward. The advantage was that it was now possible to flip to a reference without unfolding the entire document. The next development known as whirlwind binding ("xuanfeng zhuang" 旋風裝) was to secure the first and last leaves to a single large sheet, so that the book could be opened like an accordion.