How to stay on line from point to point when navigate?

[Balazs Hober]

Make sure that the Identifying toggle switched on before the layer on the Layers panel to use snapping:

Identifying
[i] Tapping toggle turns identify and snapping commands and printable legend on/off for all layers.

Source: http://wiki.digiterra.hu/en/downloads/D ... og_box.htm

Then you just need to replace the target icon on the screen to vertex by vertex of the line feature.