Ducts are found in forced air heating and cooling systems and are used to transport air. Ducts are typically constructed of sheet metal in square or round (often called spiral duct) profiles or may be flex duct. A length of ducting is referred to as a run. Ducts are used to supply rooms with air and can also return air back to the air handler. Ducts are often located in attic spaces, basement ceilings, walls, floors, or exposed in loft layouts.
Ducts terminate in grills, vents or diffusers. Between the main duct run and the vent, can be a boot. The boot is used to connect the duct to the vent, as well as provide insulation and mounting options in some cases.