In this exercise, which is a simple extension of the Measure Game, you change guards with every step. So you must be simultaneously aware of your partners steps and of the position of your sword at all times.
The guards/wards of Alber, Pflug, Ochs and Vom Tag are of greatest importance.
Master Johannes Liechtenauer tells us in his verses to fight only from these four main guards. Thus these primary wards are reliable and universal.