From the Figure Four HG it is possible to attack your opponent with a Knee Bar. In the video above the guy goes over the attack and makes a good point about driving your opponent's face into the mat.
As this guy explains the tech he stops half way through the technique with his shin across the opponent's midsection. I wouldn't advise doing this because you can get submitted with a heel hook by your opponent.
It is better to cut all the way across without the added step. This will protect you as well as add to the surprise factor increasing your odds of landing the knee bar.
