This tool allows the perpendicular distance between any two parallel entities to be calculated. The entities must be of the same type and parallel (for the purpose of this tool arcs and circles are the same type).
After activating the tool, identify the first entity. Then identify the second entity.
If two parallel entities are identified, the measured distance will now be displayed on the Edit Bar and in the Output toolbox. If the entities are not parallel an error message will be displayed.