There is very little said about this type of a siege, except that it is rare and similar to halpschilt. In my oppinion this is a false edge cut from above. This kind of attack is a bit uncomfortable to do (and so rare), but will strike from above as halpschilt and thus can be handled in the same way. It seems to be matching the image (bent albow) and also the text (can be defended in the same way as halpschilt).
This siege is presented in the play 31