Keep your slave on his knees with his balls trapped!
Lock your slave's pathetic balls in the Humbler and cuff his ankles so that he is confined to the ground at your feet... where he belongs. Knobs on either end of the wooden vice allow you to open and close the Humbler, pulling his scrotum through the hole. Curved to fit under his asscheeks, this evil instrument will ensure that he can't stand or straighten out without extreme discomfort. The ankle cuffs easily clasp onto the Humbler for optional use, further restraining his movement and position. Their comfortable lining allows him to focus all his attention on his tormented balls. You can even further his incarceration by putting locks on the buckles, so that he is completely at your mercy!