Sheet Metal Journeyman Practice Test

A circular take-off is a branch connection in ductwork that taps air from the main run into a branch duct. Its purpose is to attach to the duct and deliver air to a location such as a diffuser or register. It isn’t primarily used to seal joints, dampen sound, or measure airflow—those roles are filled by sealing methods, acoustical treatments, and flow-measuring devices, respectively. So the idea that it attaches to the duct to deliver air to a location captures its main function.