The physical length of something laid flat.The lay length of a twisted pair cable, for example, refers to the length of the individual conductors if the pairs in the cable were to be separated and untwisted, and the individual conductors were to be laid flat. In a Category 5 (Cat 5) data grade cable, for example, each of the four pairs has a slightly different twist ratio, i.e., each pair is twisted slightly more or less than any other pair in the cable.Twisted, the pairs are the same length; untwisted and laid flat, they are not. See also Cat 5 and twisted pair.