Those condemned have their heads sticking out of holes braced in between by 2 inch thick planks (metal or wood, hard to tell) that stick out from the planes of the holes, yet when the giant slicer makes its cut, the severance is made on the plane of the holes, not 2 inches out from the holes in plane with the braces. If the blade has to swing past the braces, it cannot cleave inward 2 inches to make its cuts on the plane of the holes.