US Patent 8020353 Polymer building products

In polymer building products, such as polymer siding, polymer roofing, j-blocks, gable vents, etc., characterized by fastener apertures each comprising an elongate slot bounded by a peripheral wall defining the slot, the peripheral wall having a height, a fastener centering-guide comprising a layer of material extending into the elongate slot from the peripheral wall thereof, the layer of material having defined therein (a) an elongate opening that is generally parallel to, but of smaller transverse dimensions than, the elongate slot, and (b) a predetermined location, defined intermediate the length of the elongate opening, for receiving a fastener therethrough, and wherein further the layer of material is characterized by a thickness that is less than the height of the peripheral wall and sufficiently thin so as to permit relative movement between a fastener extending through the centering guide and the polymer building product.