Spanner"s designs included dining and lounge chairs, tables, and modular storage units. His furniture lines were sold and distributed at department store chains and independent merchants. "The Ruspan Originals line was boxy and geometric, but most of all it was simple, functional and modern, all qualities that appealed to young post-war couples buying furniture for their new houses or apartments." Spanner"s designs utilized innovative manufacturing techniques such as curved plywood and non-upholstered, woven-web seating.
Many of the designs reused components and shared consistent proportions, which gave his work a characteristic aesthetic.
Among his three residential furniture lines (Ruspan Originals, Catalina, and Pasadena) the Lounge Chair with Arms has been described as the "best-known and most desirable" design.