From A.D. 1004 to 1048, Bi Sheng, an engraver in the Northern Song Dynasty, made a rectangular long column with fine and sticky clay, carved characters on it, and put it into a kiln to make it into movable type. Then, according to the content of the article, put the words in order, put them on the iron frame to make a printing plate, and then put them on the fire to heat and flatten them, and you can print. Take off the movable type after printing and use it next time. This improved printing is called relief printing.