Ostracon is the word that archaeologists use for the flakes of limestone that Ancient Egyptians used as notepads. A clean, fresh break in the limestone from the hills of Western Thebes often exhibits a flat surface ideal for writing out lists, making notes, and for sketching.  They were often used by students and apprentices to practise their drawings. 

Ancient Egyptian artists achieved harmony and continuity– some might say monotony and endless sameness – over great expanses of wall by making use of a grid, so that several drawings of the same image could be assured of identical proportions regardless of size.  Occasionally, archaeologists find ostraca in which one drawing was done by a teacher or master, while the other is a copy by the student apprentice. Although these drawings differ slightly from one another, both are so fine that it’s difficult to guess if one was the work of the master and of one the student.