Instep borer
The instep borer was a medieval German instrument of torture that externally resembled an iron boot. It was hinged to permit the free insertion and removal of the bare foot. A crank projected from a housing over the instep, which concealed a long, thick, serrated iron blade, grooved so as to inflict maximum damage and promote liberal blood flow.
Turning the crank slowly advanced the blade into the boot, punching a hole through the center of the instep. The resultant wound was so large that it was not unusual for the prisoner to die of toxaemia soon after.
The fact that this device is recorded only in [1] leads to the conclusion that it was only in use at Nuremberg. It is troubling, though, that the catalog [2] which Hirsch purports to document makes no reference whatsoever to the instep borer among its thousand-plus catalogued items, leading to the possibility that the instep borer may have existed only in fantasy.