Built with plywood. Precision saw cuts for tightest fit to quarter round and square walls. Needle-sharp - rust resistant nails spaced for handling and strong enough to withstand a full power stretch. For Wood - "C" pin only for plywood, particle board orhardwood floors. Ringshank nails polished for visibility and prestarted to assure a straight drive. For Concrete - "C" pin only for concrete floors prestarted with hardy tempered nails to penetrate without splitting concrete and to ensure a solid anchor.