This is called the lower bind and the strong key. With this bind, armoured or unarmoured, I can kill you, because in all your vulnerable places I can wound you. And having made this bind, you cannot escape. And whoever is caught like this is in trouble and is having a hard time of it, according to what we see drawn in the picture.
The 5th scholar of the 3rd master of dagger makes the culminating point of a subset of plays which are all variations on the lower bind. The 2nd, 3rd and 4th scholars have all made the same entry and starting move, but completed the play before fully locking the bind on. The 5th scholar can be considered the base move of this sub set of plays. If you master this one, you can perform all the others.
Make the cover of the 3rd master, using a hooking block with your right hand to control your opponents left hand, and stepping to the outside of your opponent. Put your left foot slightly behind your opponents front foot. As you step through, place the palm of your left hand against the back of your opponents right shoulder or upper arm.
In a continuous movement, arc your right foot behind you so that you are left facing the direction you came from. This has the sensation of spinning past your opponent. Lift their hips up and out of the way as your right foot lands. You want to occupy the space previously held by their centre of balance.
As your weight anchors onto the floor, push down with your left hand. Keep the momentum of your spin going with your right hand, folding your opponents arm over your left and onto their spine. Although different people will have different amounts of flex in their arms, the higher you can put the hand up the spine, the tighter the bind will be. Your right hand is free for whatever action you feel appropriate and you will be in the position drawn.
Keep your hips pushing against your opponent and keep their head pushed down. To apply pain, lever their elbow up using your left arm. They really are in trouble and having a hard time of it. You can hold your opponent still on the spot. You can run them forward and ram their head into an obstacle, spin them to the ground, or lever their arm up so high that it dislocates the shoulder. You can grab the head with your free hand and knee them, or adjust your distance slightly and kick up into the face. You can either draw your own dagger or steal theirs, and stab them pretty much anywhere you choose.
Fiore points out that you can wound them in all their vulnerable places. They are at your mercy. Be creative.