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PolyCAD

Insert into Surface

This option allows the selected curve (or curves is choosen from the Multiple Selection Right-Click menu) to be inserted into a surface that is not already a member of, i.e. its a new curve,The submenu will display all the available X-Topology surfaces which do not contain the selected curve.

Remove from Surface

This options can be used to remove the selected curve(s) from an X-Topology surface reversing the "Insert" operation discussed above.