Basically, a loom is a simple frame for constructing the rug foundation and the facing or pile. It consists of two horizontal bars held apart by two more perpendicular or vertical bars. The vertical warp yarns are then wrapped around the horizontal bars in close parallel rows. Horizontal or weft yarns are then passed in alternation over and under each adjacent warp. This constitutes the foundation of the rug for pile pieces. The loom may either be erected vertically, a 'vertical loom, 'or it may be set up parallel to the ground surface, a 'horizontal loom.' The former type is used by village and city weavers. The latter type is typical of nomadic, tent-dwelling weavers. For longer pieces the warps may be extend repeatedly and indefinitely by tying on additional lengths of yarn, while the lower horizontal bar can be rotated as a roller, both to maintain the tension on the warps, and to roll up the portion of the rug that has been completed.
