Since there's a limited amount of time that we can be on our back in guard in judo, we have to really move quickly and show progression. Here is an instructional that will help you break down sankaku from the guard position.
Starting from guard:
- stuffing the arm through so we're figure fouring around the arm and neck (keep in mind that you can't do a leg submission around just the head, you have to have both the head and arm in)
- make sure you're heavy on the top leg (right leg in video), so they can't posture up
- left foot is going to their hip create an angle
- under hook with right arm under their leg
- pass their trapped arm over to your right hip
- squeeze knees together for the choke or go for the arm bar from that position