Rhino Guard Above Ground Swimming Pool Liner Shield Protector Pad (21-Foot Round) Defends your liner against cuts and punctures from rocks, roots, grass and glass Cushions the floor of your pool creating a soft pool bottom for your feet to enjoy Resilient geotextile fabric permits moisture to safely pass through it Liner Shield is mold and mildew resistant Easily installs on top of soil or sand bed beneath a vinyl liner