Easy DIY installation which adjusts to varying floor heights. Can be positioned after hard surface floors and adjoining floors have been installed. Hidden fasteners for safety and better appearance. Use with hard surface floors, vinyl floors, and carpeting. Aluminum. 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.