USG, the maker of the world's top brand of wallboard, is one of the largest building products manufacturers and distributors in the US. The company operates in four divisions. Its gypsum unit, which accounts for about half of sales, manufactures wallboard, gypsum fiberboard, and other products for finishing interior walls, ceilings, and floors under the SHEETROCK, DUROCK, AND FIBEROCK brands. The ceilings division makes ceiling systems and acoustic tile, used mainly in commercial buildings. USG's distribution arm distributes building products through L&W Supply. In 2016 the company agreed to sell L&W Supply to ABC Supply for $670 million.