These are actually very big screws, not bolts. Some people seem to think that if it’s big, it’s a bolt. But a bolt doesn’t have a head that can be used to tighten. It can only be tightened by a nut on the thread end, like a carriage bolt. Screws can be tightened by using the head, or the nut on the thread. Sometimes both ends need to be used. I always wanted to be a mechanical engineer and work with this kind of automation, but I was unfortunately unable to grasp the concepts of mathematics, the primary requirement for an endeavor of this magnitude. With such large sizes, it makes no sense to make a hex nut. Tightening large nuts is not done with a telegraph pole-sized wrench, but by other methods using hydraulics. For this purpose, the nut is of the usual round shape with holes and grooves for the hydraulic tool.