underlay

A synonym for padding or rug cushion. It usually describes the layer of fabric of sponge rubber or hair placed underneath a carpet or rug to provide it with longer life, to give it a more luxurious appearance and feeling, to prevent the rug from slipping, and to make the rug softer and more cushiony. Carpet padding is made of cattle hair, rubberized hair, rubber, and combinations of jute and cattle hair, as well as some man-made fibers. Sec: rugs and carpets, padding, and rug cushion.