Probably the most effective escape to deal with potential sexual assault whilst on your back. The most common instinctive response from women and men whilst fighting on their backs is to push up. This will not be effective and the attacker has gravity on their side and to bench press the average weight of a man is not easy to do. The wedge technique takes into account one of the basic concepts of any ground fighting martial art which is the instability of the attacker from side to side. The more they push down the weaker they become at the sides.
Utilize this weakness in their structure and you will escape every time.