Selvage denim (US) or Selvedge (UK) is a type of denim which forms a clean natural edge that does not unravel. The selvage edges are along the out-seam of the jeans, making it visible when cuffs are worn and visible or invisible at the pocket. In the early years of denim production the fabric was woven on shuttle looms, from a single thread, and with self forming natural edges at the sides (self-edge). Shuttle looms weave a narrower piece of fabric, and thus a longer piece of fabric is required to make a pair of jeans (appr. 3 yards / 2,75mtr). The selvage edge is usually stitched with colored thread. Fabric mills used these colors to differentiate between fabrics, Levi's was red, Lee was yellow and Wrangler was green. However, as denim became more and more popular in the 50s, and mass production became the focus of jeans manufacturers. The old shuttle looms were replaced by projectile looms. These new looms were capable of producing denim faster, and in bigger quantities, however the produced fabric was not woven from a single thread anymore, and lost the self-edge.
Today, selvage denim is valued for its irregularities and character, and is typically more expensive than regular denim. Selvedges in jeans usually denote high quality denim, albeit there are many factors to consider with denim quality.