2 Part Technique - It is important, for reasons of safety and avoiding serious injury, to keep your knee locked tensely if your opponent underhooks it from Closed Guard Standing. Otherwise, you run the risk of damaging ligaments in the event he drops his hip-weight in a direction not anatomically supported by your body. The best option is to not let him even gain a solid grip around your ankle by kicking forward, then stepping back out of range while you pry off his guard. If he is able to cross underhook your other ankle, reach for the Cross Arm Trap from either standing or kneeling, and break his Closed Guard by pushing on his knee with your free hand.