Mechanical discipline Join tool recognizes which discipline is active when in use. The tool's tee intersection joining behavior exemplifies the discipline specific outcome. In the HVAC discipline, the join tool stretches the connecting duct close to the tee intersection, and inserts a takeoff fitting. In the plumbing discipline, the join tool stretches the pipe close to the tee intersection, creates a break in the pipe to be connected to, and inserts a tee fitting. Similar behavior is seen throughout the application. The rules governing the behavior are determined by the settings files controlling automatic placement.