We go by a term called the codex, where they would have two heavy pieces of wood which become the cover, and then the pages in between would then be stitched along one side to make something that was relatively easily transportable.
Lo conocemos con la palabra "códice". Se trata de dos piezas pesadas de madera con las que se formaba la tapa, y las páginas dentro se cosían por un lado para armar un libro que fuese relativamente fácil de transportar.