‘Shag’ rugs refers to how they’re made but not what they’re made of. So like other carpets or rugs, basically any material that can be woven can be used—synthetic fibers like nylon or rayon, or natural fibers like cotton or wool.
For centuries, the ‘original’ shag rug—the flokati—has been made of tangled goat’s wool in Greece. Traditionally made without dyes they’re notoriously known to be the natural, virgin hue of the wool. More recently however wool shags can be found in any color or mix of colors.
To make a shag rug, strands or yarns of material are loosely woven—horizontal weft through vertical warp yarns. In contrast, standard pile rugs are more tightly tufted, ie. yarns are ‘passed through’ a woven cloth backing, usually with more and thinner yarns per square inch making them more dense and crew-cut like.
Typically manufactured by making loops in the weaving process, shags yarns are then trimmed at a longish length, ie. creating a deep-pile, that gives the rug a lush and shaggy look. And when the weaving is completed, the warp yarns are cut from the loom and those vertical edges are finished.