Sailcloth is woven in two forms: balanced and unbalanced. The yarns in balanced cloth are the same diameter and weight in lengthwise (the "warp") and across the width of the cloth (the "fill"). Unbalanced means a heavier yarn is used in one direction. Most moderns sails are "crosscut", which is an unbalanced technique where the heavier yarns is in the fill. This allows greater loads to radiate up from the clew (back lower corner) along the leech (back edge). This is especially true of mainsails and high aspect jibs.