In today's jargon it would be called 'Hands Free' Masturbation.
As a young lad I found that by pushing my hard cock between and gripping it with my thighs and then with my thighs making a grinding motion the same effect could be achieved as with the common hands on jerking off method. Not only was the feeling of having my cock between my thighs sensuous but also with a grinding and writhing motion I could achieve a very much enjoyed wank. I found it to be a very exciting way to masturbate especially when writhing naked over the bed. This literally left two hands free for caressing my butt, rubbing my nipples and exploring the rest of my body. This method did have a drawback in that it needed more cleaning up afterwards, have been accused many times of starching the sheets. Still use this method occasionally until now. On the other hand it saves you from WWS (Wankers Wrist Syndrome).