Floor surfaces under indoor-climbing equipment and platforms over 20 inches in height must have a unitary shock-absorbing surface that will effectively cushion the fall of a child. The surface must be installed in the use zone and maintained according to the manufacturer's directions. See §746.4801 of this title (relating to What does Licensing mean by the term "use zone"?). Carpeting alone, even if it is installed over thick padding, is not an acceptable resilient surface.