Make Overexcavate Surface From Screen Entities
This command makes the overexcavate surface from entities on the
layers defined as Overexcavate in the Define Layer
Target/Material/Subgrade command. The resulting surface of Make
Overexcavate Surface is stored in a triangulation file that is
named with "-ox" appended to the current drawing name.
Prerequisite: overexcavate entities
Keyboard Command: mk_overx_tin