The first play for Meyer’s dagger assumes that both fencers are using reverse grips and that you are in Oberhut, the High Guard.
This parry is against thrusts to your left side.
With the point down, catch the opponent’s wrist on your blade.
Immediately wind the point under, around, and over the opponent’s wrist. Doing so will allow you to pinch his wrist between your blade and wrist. As you do this, pull his dagger arm down to your right side. This will unbalance him, leaving you free to counter-attack.
The textbook move that follows is a pommel bash to the chin or face. But if you constrain his arm with your off-hand other attacks become viable.
Meyer continues with a rather brutal finishing move,
Now if he goes up after your dagger, then pull it around your head, and thrust horizontally inside against his right arm through to his face. And finally slash straight from above through his face, with a back-step on your left foot.
The technique is summarized as,
With the first you catch his wrist on your hanging dagger, strongly away from you toward your left.