Underlay for Ponds by Geotextile, 15feet wide, sold by the linear foot.

Geotextile fabric underlay for ponds adds an extra protective barrier between the pond liner and rocky soil. It makes all pond liners more puncture resistant and stabilizes the ground under the liner to keep EPDM and other liners from over stretching.
Quick and easy to install. It is sold by the linear foot- eg; 1 foot by 15 feet wide.