The idea that Don is trying to explain with the neck lock is pretty simple (if I know what he's talking about). What he's doing is separating the head from the spine by changing the angle, this removes all of the support that the neck and back might otherwise give it.
That's a pretty cool, I've never had the opportunity to use it as a takedown, but when standing it seems to work pretty well for landing knees and elbows.
Sig by Toxic
Barnett - Toquinho -Werdum - "Nurmie"
Z. Gurgel - Morango - Rocha - Tiequan