http://www.theonion.com/articles/original-handjob-patent-document,18895/
This original schematic shows the mechanics behind the handjob as registered with the U.S. patent office. Amazingly enough, the technique has changed very little over decades of use.
Related: This Day In History: The Invention Of The Handjob
There is a 5-10 minute video to go with this.
It is a segment on the new Onion News TV show.