Going Through in Attack and Defence
Meyer's dagger section provides a number of precepts; general principles for dagger fighting.
The second precept instructs us on Going Through. For example, if we are attacked from above we "punch" our dagger hand up under his descending arm to the outside, deflecting the arm away to the side and attacking to the fact with a thrust as his arm goes down.
We can also go through with the blade with a parry. For example in the Parry from High Guard 2 and Parry from Low Guard 2 we see a parry of the wrist with the dagger which then goes through underneath and traps over the other side using the First Precept
Likewise if we're attacking and he parries it, we can corkscrew underneath his parry before it lands and go through, attacking with a thrust from a different angle. We are advised to guard with our left hand while doing this to prevent counterattacks.