These pads are used when one wants to limit the movement in a piece of carpet. This pad can be made from jute, or hair mixed with jute, or synthetic fiber, or recycled textile fiber. Most often these pads are used under area rugs, under commercial carpets, and under some berber carpets. The key here is density. Spun nylon is best. Stay with at least 7.5 lbs per cubic ft. density on the synthetic fiber, and 12 lb density on the jute pads. Thickness should be between 3/8 and 7/16 inch. Total weight should be 40 ounces per square yard.