A thin hardboard, typically 1/4 inch, that comes in 4X8 sheets and is readily available at most home improvement stores. The "tempered" type is extra-hardened, much less flexible (short pieces are inflexible) and more dense that standard masonite hardboard. By comparison, tempered hardboard is often "darker" in appearance than standard hardboard and is usually smooth on both sides. On many standard hardboard sheets, one side is smooth, the other side is rough.
