Process that mats together fleece (raw wool ) by subjecting it to moisture, heat, friction, and pressure.
Sheep hair have scales that open somewhat when wet; layering hairs in a parallel fashion and applying some form of agitation cause the hairs to tighten together in a solid mat. The result is a lightweight, windproof, and water-resistant fabric that has been used for millennia to make hats, boots, and tents. Light felting is sometimes done to woven or knitted wool, a process known as fulling , to create a thicker and softer fabric.