Joint compound also known as drywall compound or Mastic which is a white powder of primarily gypsum dust mixed with water to construct a mud the consistency of cake frosting, which is used with paper or fiber joint tape to seal joints bet ween sheets of drywall to create a seamless base for paint on interior walls. It is often referred to simply as mud or as joint cement .

Joint compound can avoid almost all imperfection from the surface of drywall including damage, fasteners, holes, drywall tape, bumps, tears, and other minor damage. It can also be used to finish gypsum panel joints, corner bead, trim and fasteners. .