Why is calligraphy called a book list?

Write directly on stone tablets or other hard objects with a brush dipped in cinnabar. "Shu Dan" is a very common calligraphy learning term, which refers to writing directly on stone tablets or other hard-faced objects with a brush dipped in cinnabar. Generally speaking, Shu Dan is a process in which craftsmen carve words on the stone before carving the tablet, and then carve words on hard-faced objects with a knife.