Trained as an industrial designer and a sculptor, Castle was part of the American studio craft movement that emerged after WWII. He is best known for his works in wood that blurred the boundary between furniture and fine art, but he designed objects to be made in multiple media including plastic, metal, concrete, glass, and stone. He used a variety of crafting techniques including hand-carving stack-laminated wood, casting, and computer-controlled CNC milling. He was a long-time faculty member of the Rochester Institute of Technology.