The outside edges of most bolts of fabric are smooth, in contrast to the raw edge, where threads can be pulled and unraveled. The smooth edges are the selvage, or selvage line.
The selvage is the finished edge of a fabric, usually of a tighter weave than the rest of the fabric.
The threads that run the length of the entire bolt of fabric are called lengthwise threads, and they form the lengthwise grain. The threads that run the width are the crosswise threads, and they form the crosswise grain.
Creating a Selvage
The selvage is created when the crosswise threads turn on the fabric’s outside edge. Because the thread runs continuously back and forth across the width of the fabric, there are no ends at the edge, and the selvage doesn’t fray or unravel except when cut.
Manufacturing information such as design number or type of fabric may be printed on a selvage line of mechanically woven fabric.
The word “selvage” originated around 1460 and comes from a combination of the words “self” and “edge.”