He stands in a squatting stance and completely supports the woman's body by her waist.  She uses her legs against his waist to remain suspended in front of him while holding on to his elbows to pull her body up to maintain a horizontal position... all while having sex.  Just trying to describe this position has a difficulty level of very hard.  Needless to say, this position requires both the man and the woman to be in extremely good physical condition.