A longitudinal model of half of a vessel's hull. In the 19th century, it was a primary design tool, with most American sailing vessel designs starting out as carved half models, from which dimensions for the full-sized hull would be taken. Some of these were turned into decorative half models by putting them on a backboard and adding deck houses. In the late 19th and early 20th century half models were used to develop patterns for iron or steel plates that made up the hull. Today half models are made from paper drawings as decorative pieces.