This is one technique, although (confusingly) shown with the defender holding the dagger in the left or right hand. Both work.
Points of attention:
- Think of picking up a coin.
- This works best against an attack to the second opening.
- While I did not demonstrate, the plate shows you throwing up your legs, falling with your full weight on his arm (probably breaking it). This is not very nice, but not doing so leaves you vulnerable to him lifting your left leg, negating the technique.
With the dagger in the other hand: