A Guide file is a
GPX file.
This is a standard format to describe routes and special locations.
The core of a GPX file is a set of coordinates describing the route to follow while cycling.
In Cyclist Erik these coordinates are shown as yellow arrows on the blind map.
The GPX file also can contain special locations (waypoints) in this case Cycling Points (Fietsknooppunten).
These are shown in Cyclist Erik at the upper right section of the page.
For each cycling point the distance to that point along the route is being shown.
If the GPX file does not contain cycling points, they are still shown on the blind map, but the distance along the route will not be shown.
A GPX file can be created with route planners.
Most route planners have the feature to store the route as a GPX file.
For the Netherlands you can use
Routeplanner Fietsersbond. For Belgium you can use
FietsnetStep by step description how to create a GPX file for Cyclist Erik