The traditional washboard is usually constructed with a rectangular wooden frame in which are mounted a series of ridges or corrugations for the clothing to be rubbed upon. For 19th-century washboards, the ridges were often of wood; by the 20th century, ridges of metal were more common. A "fluted" metal washboard was patented in the United States by Stephen Rust in 1833.[1] Zinc washboards were manufactured in the United States from the middle of the 19th century.