Specify Hidden Line Settings for Duct
Use the Hidden Line pane of the Mechanical Settings dialog to specify how ducts that cross each other (in separate planes) are presented in the model.
About Duct Settings
When Duct Settings is selected, the right pane displays a set of parameters that are common to all the duct systems in a project.
About the Duct Size Dialog
Use this dialog to add a sizes for rectangular, oval, and round duct sizes to a project.