Default parts are the parts automatically inserted by the software as you lay out runs of duct, pipe, cable tray, or conduit. You can change the default parts during layout.
If you use systems in your designs, you can define different default parts for each system. During layout, if you need to add a part that has no default defined, the software prompts you to select a part to use.
You can also specify the plumbing fittings used by default for plumbing system definitions.