A tartan is a specific woven pattern that often signifies a particular Scottish clan, Irish County, or District in the modern era. The pattern is made with alternating bands of coloured (pre-dyed) threads woven as both warp and weft at right angles to each other. The weft is woven two over - two under the warp, advancing one thread each pass, forming diagonal lines. The resulting blocks of colour repeat vertically and horizontally in a distinctive pattern of squares and lines known as a sett. Traditional kilts almost always have tartans. Tartan is also known as plaid in North America, but in Scotland this word means a tartan cloth slung over the shoulder or, it means a blanket.