Designed to fasten and finish the edge of cloth or jute-backed carpet. Made from extruded aluminum. Screw nails included. Carpet metal installation on concrete surface suggestion: Drill a hole in the concrete, insert a 3/16" x 1-3/8" or 1/4" x 1-3/8" wood dowel. Use the screw nails provided with carpet metals, insert into dowel, expanding the dowel to lock in place.