Weaving is making a fabric by interlacing two or more sets of threads. In "plain" weave, one set of threads – the warp – extends along the length of the fabric; the other set – the woof, or weft – is at right angles to the warp and passes alternately over and under it. Other common weaves include "twill," "satin," and "pile." In basic twill, woof threads, stepped one warp thread further on with each line, pass over two warp threads, under one, then over two again, producing diagonal ridges, or wales, as in denim, flannel, and gabardine. In satin weave, a development of twill, long "float" threads passing under four warp threads give the fabric its characteristically smooth appearance. Pile fabrics, such as corduroy and velvet, have extra warp or weft threads woven into a ground weave in a series of loops that are then cut to produce the pile. Weaving is usually accomplished by means of a hand- or power-operated machine of loom. Warp threads are stretched on a frame and passed through eyelets in vertical wires (heddles) supported on a frame (the harness). A space (the shed) between sets of warp threads is made by moving the heddles up or down, and a shuttle containing the woof thread is passed through the shed. A special comb (the reed) then pushes home the newly woven line. See also textiles.