the replies denying that you can even do that are self reporting themselves so hard 

allow me to explain for those uneducated: 

when you hit it from the back hard af and fast it creates almost a clapping sensation/motion right on the nuts and on their clit . it has almost a sting to it. like imagine clapping your hands hard and fast for a solid two minutes

it *almost* hurts but when you’re in that zone the pain feels so good. the picture is a perfect visualization