The frame on which the warp (vertical) threads are strung first and held under tension so the weft (horizontal) threads can be interlaced through them and the knots tied onto them. Hand-knotted rugs are made on simple looms, from those set up in weavers' homes to the compact, transportable ones of nomadic weavers, where every knot is tied by hand. Loom size sets rug size: nomads' small looms typically yield rugs no larger than about 4 x 6 or 5 x 7 ft (1.2 x 1.8 m or 1.5 x 2.1 m), city workshops with very large looms weave palace sizes, and the number of looms a workshop runs gauges its scale. Wooden looms in tribal and village weaving expand and contract over time, one cause of crooked rugs. Power looms such as Wilton, Axminster, and Jacquard, the industrial descendants, make machine-woven carpet.
A rug produced by industrial machinery, typically on power looms, rather than knotted by hand, usually from synthetic fibers such as polyester, polypropylene or nylon, and finished in hours rather than months. Its design looks perfectly symmetrical yet slightly fuzzy, and its edges measure almost exactly alike. The back feels stiff and plastic-like, with a regular honeycomb texture on which the pattern cannot be read. Any fringe is a uniform synthetic trim attached at the end of production, and some rugs have none, unlike a hand-knotted rug, whose fringe is its own foundation threads. Machine-made rugs are less expensive, of lower quality and wear out sooner, and are not authentic Persian or Oriental rugs.
An industrial loom driven by machinery rather than by a weaver's hands, on which machine-made rugs are woven through an automated process, typically from synthetic or machine-spun yarns. Because no one ties knots by hand, the design comes out perfectly aligned and symmetrical, the back feels stiff and plastic-like, and the pattern and colors cannot be read from it as they can on a hand-knotted rug. The process is faster and less labor-intensive than hand-knotting, giving a less expensive rug of lower quality.