Most of the new building materials on the market today are either plastics or composites — alternatives that combine unlike materials in new ways. To make these products saleable, manufacturers design them so that they can be worked and installed with traditional tools and skills. In many cases, the raw materials come from what has traditionally been considered waste. Wood I-joists, for instance, are made from glued-together veneers and chips from small-diameter trees. And the makers of medium-density fiberboard (MDF) take wood chips from mill waste, break them down to their individual fibers, and glue them back together under heat and pressure. The process yields a paintable panel with enough uniformity and dimensional stability for use in both cabinets and furniture. But wood