Woven Roving is strands of glass fiber grouped together to form a twisted yarn. The roving is then woven into a coarse, square, lattice-type open weave to form the material. Woven roving provides great tensile and flexural strengths and a fast laminate buildup at a reasonable cost. It is more difficult to wet out than chopped strand mat or cloth however, and because of the coarse weave, it is not used where surface appearance is important. A layer of chopped strand mat is used between each layer of roving to fill the coarse weave when more than one layer is required. Woven roving is categorized by weight per sq. yd. and is sold by the running yard.