Redline selvedge denim is denim where the self-finished edges has red yarn yarn in between the white edge yarns.
The coloured yarn was originally added to help manufacturers recognise the different qualities that they were producing for different clients.
The Cone Mills White Oak factory in North Carolina started supplying fabric for Levi’s in 1915. Around 1927, they incorporated a red yarn in the selvedge of their brand’s extra durable XX-fabric to make it easier to distinguish it from other qualities.
Today, the red line has become synonymous with selvedge fabric from any brand, which may be partly due to the dominance of Levi’s in the market the first half of the last century.