A recommended action to do as a defence against halpschilt siege (a cut to the head) if the defender was in prima or tertia custodia, or priest's special longpoint.
So the prerequisitive is the attacker closing in from out of distance with a downwards cut. The defender wil step back and extend the distance, so that his head is safe and the attacker cannot hit it. At the same time he will push both his hands forward, sniping the attacker's hand from his right side. Defender's hands are covered by the shield, so they are protected and can receive a hit from attackers halpschilt. Defender holds his hands pretty low, which is important for followup.
The whole action can be viewed as an in-tempo counterattack aimed at the attacker's hand. The hand snipe might miss (especially if the attacker also holds his hands low), but the ending position is also desirable by itself. At the end of falling under, the attacker has a direct way for possible thrust against the head of the defender. But this is kind of a trap - if the attacker goes for the thrust, it is easily defended by stichslack, that will instead hit the attacker. If the attacker just waits and does nothing, the defender can still do the same thing and hit the attacker with stichslack from his own initiative. This usage of stichslack are covered by play 30 and play 31