Working with Markups > Annotations > To Create a Surface Polygon
  
To Create a Surface Polygon
1. In the Model View, click Markup, and then click the arrow under Shape. The Shape menu appears.
2. Click polygon or shaded polygon. The pointer becomes a drawing pointer.
3. To place the vertices, select points on the surface of one or more parts.
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All vertices of a surface polygon must be on the surface of a part.
4. To delete the last vertex you placed, press DELETE.
* 
You cannot delete the first vertex using this method.
5. To close the shape, double-click. The surface polygon is created.