The over under pass is a technique that's gained a lot of momentum lately since Bernardo Faria brought it back to the spotlight in 2015. By using specific grips, excellent pressure and beautiful technique you too can pass from the over under without getting triangled! The Over-Under pass starts with establishing a "Four Finger" grip around the end of the pant leg with the arm on the side you are passing to (If you are passing to your left, it will be your left hand controlling). The opposite arm dives underneath your opponents leg while at the same time bringing your head to the opposite hip of your opponent, closing space and keeping pressure.
With your grips and control established sprawl your legs back while at the same time taking your opponents pant leg and pushing it back, flattening their leg. Bring your legs around to the pinned leg side (the side initially aiming to pass) and work towards the torso of your opponent to establish Side Control.
Making sure that you stay close to your opponent and maintain constant pressure on them will increase the likelihood of success with this pass. Bringing your head to the opposite side is important as it helps keep your opponent flattened out. Adding this pass will make your Top Half Guard game that much better.