From AKBAN-wiki, the Martial Arts Database

Juji gatame (arm bar) from the guard is a signature move of Brazilian Jiu-Jitsu. Here is the basic set up from the guard:

1. Left hand secures opponents right hand tightly on your chest.
2. Right hand comes under opponent's left hands and cups behind his right elbow to ensure elbow does not drop to the mat.
3. Left leg posts on opponent hip while left knee pushes into opponent's shoulder to ensure his hand does not jerk out.
4. Hip moves slightly sideways and diagonally using left leg as base and right leg scoops left putting downward pressure behind opponent's shoulder and on his back.
5. If opponent's head drives toward you then switch hands: right hand slides down on his hand and eventually grabs his right hand and left hand pushes his neck and head away.
6. Once the head is far enough, the left leg goes over opponent's head putting downward pressure on head.
7. The arm is broken by pressing downward with both legs and slightly raising the hips.

Video of the technique

This technique is part of Budo Ninjutsu Grade requirements syllabus Yellow belt grade requirements, Orange belt grade requirements, Green belt grade requirements and of Black Belt grade requirements