Duck is a lightweight canvas usually made of linen, cotton, or synthetic fibers in a plain weave. Duck is woven in many widths and weights. It is strong and waterproof. The fabric is used for the aprons of cooks, waiters, and butchers; for the uniforms of dentists and surgeons; and for shower curtains, pressing cloths, and tennis shoes. The heaviest grades of duck are used to make conveyor belts, boat sails, mailbags, tarpaulins, and tents. See also Canvas.