Using the wide, flat tip of a special trowel, they spread the joint compound into and along each side of the joint with brushlike strokes. Nail and screw depressions also are covered with this compound, as are imperfections caused by the installation of air-conditioning vents and other fixtures. On large commercial projects, finishers may use automatic taping tools that apply the joint compound and tape in one step. Finishers apply second and third coats, sanding the treated areas after each coat to make them as smooth as the rest of the wall surface. This results in a very smooth and almost perfect surface.
Some finishers apply textured surfaces to walls and ceilings with trowels, brushes, or spray guns.
Lathers apply metal or gypsum lath to walls, ceilings, or ornamental frameworks to form the support base for plaster coatings. Gypsum lath is similar to a drywall panel, but smaller. Metal lath is used where the plaster application will be exposed to weather or water, or for curved or irregular surfaces for which drywall is not a practical material. Lathers usually nail, screw, staple, or wire-tie the lath directly to the structural framework. As in other construction trades, drywall and lathing work sometimes is strenuous.