Transits

When two identifiable features on the map are both visible on the same line of sight they are said to be in 'Transit'.

If you are walking along a Line Feature and can see two identifiable features in Transit - then a line drawn on the map through the two features and back to your Line Feature will give you your position on your Line Feature.

The line of a road, the edge of a forest or a field boundary wall can provide the same information.