Workers in this unit group shape, assemble and erect heavy metal girders and plates to form structures or frameworks. Their functions include: marking metal members to guide in cutting, drilling and shaping them for use in buildings, ships and other structures; drilling, cutting and shaping structural steel in a workshop; erecting steel members for buildings, bridges and other constructions; assembling and erecting framework and other metal parts of ships' structures; shaping and fitting structural steel plates of ships under construction or repair; riveting structural metal members by hand, machine or pneumatic hammer; performing related tasks. Blacksmiths, hammersmiths and forging-press operators are classified in unit group 8-31, Welders and flame-cutters in unit group 8-72 and Reinforcing-iron worker in 9-52.30.