Most rug foundations are made of cotton because it is firm, strong, and does not buckle. A strong, natural fiber known and used for centuries. Cotton is less susceptible to humidity and subsequent stretching. Cotton strands are anchored onto specially-constructed looms to create the warp (lengthwise) and weft (horizontal) of the rug foundation. The rug-maker, sitting at the bottom of the loom, works from the bottom up, tying knots of silk or wool onto cotton cords. One of the most beautiful aspects of a hand-made rug is the cotton fringing at top and bottom. When the weaver finishes knotting, the cotton cords are cut and then knotted into fringe.