The large, single, square-rigged sail of vathmal (finely woven wool cloth) or linen cloth had an area of around 330 square feet. It was secured with sealskin or walrus skin ropes and was coloured with wood bark dyes. Apart from its decorative use, the bark dye prevented the sail from rotting. The sails were often reinforced with leather which created a distinctive striped or diamond shaped pattern. The sail was sometimes put to good use by draping it over the lowered yard-arm to create a tent which the sailors could take shelter under.