The Double Bagger is an advanced Rubber Guard technique from the mind of Sean Bollinger. Sean is a brown belt with Eddie Bravo. I had the pleasure of being able to train with him at 10th Planet Jiu Jitsu. Real nice kid.
His Rubber Guard technique is insane. You must have incredibly flexible hips for this one. I am pretty flexible but not enough to pull this one off yet.
The first video above is with Eddie and Sean at Legends Gym in Hollywood. In this video Sean demonstrates the technique.
The second video is a grappling match where Sean pulled off the technique live just in case you might think "that will never work." He uses a variation of it to set up a triangle. It starts at 2:44 of the video if you want to skip to it.