jiǎn 簡 (bamboo slips) was the main writing material for all kinds of records, from books to tax registers, before the invention of paper during the Han Dynasty.
Text was inscribed vertically from right to left with one column per slip, and tied together with two or three threads. The length of such writing "boards" was less than one metre. They were rolled up and stored in shelves in the libraries and archives. Whole books thus consisted of several scrolls that had to be marked on the outside, as to which chapters the particular scroll contained. The name of the book and of the chapter was often also written down inside, on the first slip.