Select Elements Intersecting a Polygon
You can select elements by cropping the polygon shaped area. The elements intersecting the area will be selected.
As an example, Drawing 
Toolstrip - Drawing
- Click the points of the polygon with the left mouse button.
- Select the context-sensitive function
OK.
Both the elements that are entirely inside the area and the elements that intersect the area are selected.
Note:
- You can add a new area to the selection by pressing the Ctrl key and selecting an area as above.
- You can remove or add selected elements by pressing Ctrl and clicking the left mouse button over an element.