Tommy showed us this one Saturday. Rodrigo was out with the flu, so Tommy taught a pretty solid class. Some warmups and stretching on our own (there was a new guy and Adam, who's only had three or four classes). Then three minutes of the armbar from the mount. Then he showed us an open guard sweep that we worked on for a little while. Ten minutes of passing the guard (he and Jesse Singh were "kings of the guard"). Ten minutes of maintaining the guard. Then I rolled for twenty minutes with Tommy and five with Jesse.
Here's the open guard sweep. You are maintaining the guard. The guy stands up. You want cross collar and wrist control. Feet on his hips.
Switch hands so that your inside hand is now controling the wrist. Now, you are going to swing around to the outside of the guy and ultimately take his back. To do this, swing your outer leg back toward your head as deep as possible and then swing it hard behind and between the guy's legs.
You will hook your foot around his far leg. It sounds impossible to do unless you've got long legs. But the trick is to get a good deep swing back and then kick it out and around and in between the guy's legs. Hook the top of your foot against the top of the thigh of his outer leg.
Your other leg should hook behind the knee on his other leg. With your outer hand, grab his belt at the back
The sweep: kick out with both hooks. Pull on the belt and the wrist grip. The guy should fall backwards right into your lap. Sink in your hooks and take back control.