The name Pile Driver conjures up a dramatic image! This position has the receiver lay on their back with their lower back and legs raised all the way up so that their ankles are either side of (and beyond) their own head. The exact end position will depend on the flexibility of the receiver. This position totally exposes the groin area to the giving partner who stands astride the receiver's groin to perform. The giver moves up and down on the receiver to create friction. The giver is also able to use their hands to caress and explore their partner's lower body.
This position requires considerable flexibility on the part of the receiver and it cannot be (fully) achieved by most, but it is wonderfully "naughty" due to the feeling of being totally exposed and 'giving it all'. Those less flexible might try getting into the position, but stop at the point where the position starts to become uncomfortable. The giver can also help those less flexible by using their hands to support the receiver's thighs at mid-point. The giver should be careful not to over-extend the penis beyond what is comfortable at this unusual angle (penis pointing downwards).