To draw an irregular polygonal opening in an existing surface, use the following procedure.

Tip: To assist in adding openings to surfaces, you can first click the Edit Surface tool in the Tools group on the Surface ribbon tab.

This isolates the surface in elevation view. You can also create local coordinate systems and grids for this view. Once you have added surfaces, you can then click the Edit Surface tool again to commit the changes to the physical model.

1. On the Model ribbon tab, select the Polygonal Opening tool in the Create group.
   
   The tool is highlighted to indicate that it is active. The mouse pointer changes to an add openings cursor, , and a yellow symbol "snaps" to the nearest snap point.
2. Click a point in the with an existing surface to define the start point for the new opening. A wireframe with one end anchored at the selection point and the other "rubber banded" to the pointer appears, representing the opening edge connecting two corners.
3. Click the subsequent corners to define the opening, continuing in either a clockwise or counter-clockwise order. Click as many corners as needed, so long as no edge of the opening crosses any previously defined opening edge (i.e., a regular polygon).
4. To close off the final polygonal opening edge, either:

   Double-click last corner

   or

   Click the first corner a second time

   The opening is subtracted from the physical surface.
   Note: All vertices and edges of a polygonal opening must be withing the boundary of the surface. They cannot overlap or touch any existing opening.
5. Repeat steps 2 through 5 to add as many more openings as needed.
6. To stop drawing new openings, do one of the following:

   select the Polygonal opening tool again (or any other tool)

   or

   pres the <Esc> key