This Is A Very Good Idea!

All liners require the installation of an underlayment, a cushion of material between the liner and the soil that prevents punctures and tears. Sand is a good choice for the pond bottom and other horizontal surfaces but can't be laid vertically. Old carpet and underlayment from pond dealers are ideal. Some new liners are manufactured with an underlayment already attached. They are extremely puncture resistant and can be used, for example, over coarse gravel or sharp rock.