Secures and protects the exposed edge of stretch-in carpet at doorways and other openings. For jute or canvas-backed carpets. Durable aluminum, fluted design with a mill finish. Screw nails included. Carpet metal installation on concrete surface suggestion: Drill a hole in the concrete, insert a 3/16" x 1-1/4" or 1/4" x 1-1/4" wood dowel. Use the screw nails provided with carpet metals, insert into dowel, expanding the dowel to lock in place.