“Sand molding. Irregular or odd-shaped parts that would be difficult to make from metal plate or bar stock may be cast to the desired shape in sand molds. A pattern may be a wood or metal model of the part so constructed that it may be used to form the impression, called a mold, in the sand. Molten metal, when poured into this mold and solidified, will form a casting of the desired part. The sand for the mold is held in place in a wood or metal frame, or box, called a flask. The assembly of the entire flask is shown in Figure 14.1. The opened flask is illustrated in Figure 14.2. Figure 14.3 shows a simple pattern, and Figure 14.4 shows it as it is used to form the mold.” (Blueprint Reading for Machinists, Intermediate, 6th Edition by David L. Taylor, p. 112)