Replaces surface areas removed by the SURFTRIM command.
Button
Toolbar: Modeling tool set
Surfaces - Edit tool group (expanded)
Surface Untrim
Menu:
Modify
Surface Editing
Untrim
If the trimmed edge is dependent on another surface edge that has also been trimmed, you may not be able to fully restore the trimmed area.

The following prompts are displayed.
Select the edges of trimmed areas to replace or enter SUR to untrim surfaces.
Select a surface to replace all trimmed areas.