Grids > Specify Planar Region applies a planar NURBS surface to a selected patch (or patches) on a Shape object (only after grids have been generated in the patch). The selected patch(es) must be almost planar before the function is started.
Click a patch to designate it as planar, or Ctrl-Click a patch to de-select it.
Mark Boundary As Sharp checkbox - specifies whether to leave sharp boundaries around the special planar region, or whether to smooth the shape of the joint.
Next button - applies the planar NURBS surface and prepares for the selection of an additional patches.
OK button - saves new NURBS surfaces to the patch object and closes the dialog.
Cancel button - terminates the dialog without saving new NURBS surfaces to the patch object.
Also see NURBS > Clear All.