The beginning of carpet weaving remains unknown, as carpets are subject to use, deterioration, and destruction by insects and rodents. Woven rugs probably developed from earlier floor coverings, made of felt, or a technique known as “flat weaving”. Flat-woven rugs are made by tightly interweaving the warp and weft strands of the weave to produce a flat surface with no pile. The technique of weaving carpets further developed into a technique known as loop weaving. Loop weaving is done by pulling the weft strings over a gauge rod, creating loops of thread facing the weaver. The rod is then either removed, leaving the loops closed, or the loops are cut over the protecting rod, resulting in a rug very similar to a genuine pile rug. Hand-woven pile rugs are produced by knotting strings of thread individually into the warps, cutting the thread after each single knot.