On sailboats, a sail batten is a flexible insert in a sail, parallel to the direction of wind flow, that helps shape its qualities as an airfoil.[1] Battens are long, thin strips of material, historically wooden but today usually fiberglass, vinyl, or carbon fiber, used to support the roach of a sail. They are also used on tall ships to form the ladders up the shrouds in a fashion similar to ratlines.