their interrogation methods included such things as repeated dunking in a bathtub filled with ice-cold water ; high voltage electric shocks to the hands , feet , ears and genitalia ; the use of a special nazi designed vice to crush a man 's testicles ; hanging prisoners by the wrists to slowly dislocate their shoulders ; brutal beatings with rubber nightsticks and cow-hide whips ; and slowly burning the flesh with matches or a soldering iron .