Fireside drama. As bold as a piece of sculpture, this steel backdrop adds a sense of theater — and a measure of safety for nearby plants — to the fire pit. Designed by Koning Eizenberg Architecture of Santa Monica, California, the piece is an 8-by-8 steel sheet bolted to a steel frame behind the rectangular concrete fire pit. The steel is oiled to arrest rust. Cor-Ten steel, available in sheets like plywood, 3/16 or 1/4 inch thick, is typically used for heavy-duty landscape situations such as this.