The Code of Federal Regulations, and specifically 24 C.F.R. 3280.305(d), provides that the deflection of wall, roof, and ceiling surfaces "shall not exceed L/180 (where L equals the clear span between supports or two times the length of a cantilever)." The mathematical meaning of this formula is simply that the deflection cannot exceed 1 inch in 180 inches (or 15 feet) of length. In other words, 180 divided into a length of 180 inches (or 15 feet) equals 1 inch. Thus the deflection of a span of that length, or a cantilever of half that length, could not exceed one inch. Chesser obtained knowledge of the mathematic formula through on-the-job training in the mobile-home business, including inspection and appraisal work for the Veterans Administration and the Department of Housing and Urban Development.