To mark an Edge on a photograph:
•
Pick up the Edge Marking tool 
, or select
"Mark Edges" from the ribbon toolbar’s Create
Tab‘s Marking group expand menu.
The Edge cursor will appear when the mouse is over a photograph .
• Move the dot on the cursor to a place on the edge and click the left mouse button.
An Edge Point will be placed on the photo and a dynamic line will extend from it to the cursor.
• Move the dot on the cursor to another point on the edge and click the left mouse button.
The Edge Mark will be drawn.
Note that when marking Edges you are marking along a linear feature in a photograph and you should not be marking sharply defined features that are easily seen in other photos (use Marked Points for that. The key here is when you reference an Edge between photos, their end points do not need to match.