Individual letters are assembled into words and lines of text with the aid of a composing stick, and the whole assembly is tightly bound together to make up a page image called a "forme", where all letter faces are exactly the same height to form a flat surface of type. The forme is mounted on a printing press, a thin coating of viscous ink is applied and impressions made on paper under great pressure in the press. "Sorts" is the term given to special characters not freely available in the typical type case, such as the "@" mark.