Instead of using ordinary building planks- 2x10’s, there are times when the improved extension planks are time savers. They are strong and lighter than ordinary planks in weight. Made in three sizes: 6 feet closed, opens to 10 1/2 feet; 8 feet closed, opens to 14 feet; 10 feet closed, opens to 17 1/2 feet. All are 11 inches wide.
International Association of Master House Painters and Decorators of the United States and Canada Painting and Decorating, Working Methods32