Stiffeners can be required by some ductwork specifications for strengthening the duct. There are multiple methods for stiffening, including external flange stiffening and internal tie rod application. In the Autodesk Fabrication products, you can access the database settings for stiffeners by clicking Database
Fittings
Stiffeners.
On this dialog, you can create an edit stiffeners. See Create a Stiffener for more information.
After the stiffener types have been determined, stiffener breakpoints can then be created. See Create Stiffener Breakpoints for an example of how breakpoints can be used to apply different stiffeners, based on the size of duct.