•Also called underlay cloth or underlayment
•No liner should be installed without this underneath
•Extremely thick and flexible
•Will not rot like other materials
•Strong polyester underlay protects liners from puncture
•Scanned for metal debris from manufacturing that could damage soft rubber liners
•Typically used below garden pond liners to protect the rubber from puncture by rocks, roots, and other soil debris
•Protects against puncture from objects above the liner by limiting how much the liner can stretch under pressure
•When garden pond liners are to be covered with soil, gravel, rocks, or concrete, fabric should be used both above and below the liner
•Since it does not deteriorate under a wide range of soil pH and is essentially non-biodegradable, it should last as long as our rubber pond liners
•Heat and sunlight stability makes it suitable for use under reservoir liners and stormwater retention pond liners that may be exposed to direct sunlight for extended periods when water levels are low
