HUMBLER

How many of you would find a night in a ball stock a trip worth having? I know one Trip who did. Look closely at the photos below. That wooden device you see clinging to the back of Trip's thighs is called the Humbler. For obvious reasons, it is designed to humble a man by securing his balls behind him, stretching them taut, while making it nearly impossible for the wearer to straighten his legs completely. Of course a boy will be tempted to try, but it's not long before he bends back over again to alleviate the pressure.
I have discovered there are a couple variations of the Humbler design. The standard model only has the two pieces you see here, which fit together to contain the balls.
Once screwed down tight, a groove in the wood rests against the back of the thighs, and creates resistance against the wearer (should he attempt to stand straight). There are also locks on either side for added security.
The model I found here (on E-Bay, of all places) includes a third piece, one designed to slide right into the curve of the wood (where the balls rest) and acts like a vise, simultaneously stretching and squeezing to whatever degree seems appropriate.

source: http://www.sirebound.com/gallery/Guys/Pleasure_Trip.html