Sheetrock is simply the brand name of an incredibly popular drywall product. Drywall, a panel made of gypsum plaster sandwiched between thick paper, has many vendors. Though people will call all sorts of drywall, "Sheetrock," only drywall from U.S. Gypsum Company is actually allowed to market drywall as under the name Sheetrock. So, even if the drywall is from Titan Commercial Products, Allied Manufacturing, or National Gypsum Company, people are likely going to call it, "Sheetrock."  Sheetrock was one of the first drywall products and is so popular that its name seems virtually interchangeable with drywall. Think about how often