Commentary
In this play at the very bigining we are getting a theory on 4 types of bind.
Then we see the priest trying to close-in with some kind of schutzen (not called schutzen in the text) This attempt is defended by scholar's schiltslack in a similar way that we saw in frontal arms grab play.
Then the priest succesfully gets into back arms grab. Notice that the whole time, priest's special longpoint is not mentioned. Even though this should be the correct position used to close-in.
The we see the scholar who voluntarilly discarded his weapons in order to break free from the hold, and we see his grappling action. This in fact is an attempt to lean the priest back and then smash his back directly on the ground. This grappling technique has to be effective, otherwise the priest will get out of reach, and then it will be armed priest against unarmed scholar.
In the last image, the priest is showing how he has defended the grappling of the scholar. He has raised his sword arm, turned around and pushed the scholar's arms away with his shield. This saved the priest from the hold, and naturally got him into sexta custodia, that is used in tha last image to threaten unarmed scholar.