Aquascape 10'x15' Boxed Non-Woven Geotextile Underlayment is used to protect pond liner from rocks, roots, and other sharp objects that may damage the liner. The underlayment is lightweight, spreads easily, and has a non-slippery surface, making installation quick and easy. The soft, non-woven geotextile made from polypropylene also allows for any gases to escape properly, rather than becoming trapped beneath the liner.