Braulio uses the leghook from closed guard to help him transition to high guard. During his transition, he traps his opponent's arm and then attacks it with an armbar. The difference between the leghook he has shown in the past and the variation he shows in this lesson is in the position of his opponent's arm in relation to him. In the past, their trapped arm was wrapped around the outside of his leg. In this lesson, their arm is posted on his stomach and when he sets up the leghook control, he creates a wall outside their elbow so they can't free their arm.
Links to other Parts:
Part 1,
Part 2