Recovers the trimmed part of a surface.
Access this tool from the Surface Edit tool palette:

Untrim Options
Last – Undo the last trim operation on the surface.
All – Undo all trims on the surface.
The Delete Curves on Surface options are available only with Autodesk Alias 2019.2 or later.
Delete curves that were used in a reverted trim operation (trim edges).
Delete curves that were not used in a trim operation (free curves-on-surface).
When Used in Trim or Not used in Trim are selected, this option controls the deletion of curves that are constructors for other commands.
Untrim tool workflow
The Untrim tool can either undo the trims performed on a surface one at a time, or undo all trims to the surface.
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