To my knowledge from all the historical evidence available that I have have been able to research, it appears that the victim of Roman crucifixion was either bound or nailed to a T-shaped cross that was approximately six feet high. The average Mediterranean during the Roman era was not much taller than 5 feet, so I imagine that if nails were used to secure the feet that they were driven through the heel area with the knees bent at an angle which would also allow an extremely painful process of pushing up on the nailed feet to both relieve the pressure on the shoulders and arms that were nailed through a bone in the wrists and much later in the process to allow breathing out from lungs that were being filled with liquid. It makes sense that the stake was a permanent fixed upright and that the patibulum which was carried by the victim was capable of being secured, perhaps by a keyway, after the wrists were nailed while the victim laid stationary on the ground, and used again. It would not be difficult to imagine that two strong soldiers, one on each end of the crossbeam could lift the victim, perhaps even assisted by a third positioned behind the upright, up and over a protrusion that matched the keyway on the patibulum and let gravity take over. A cornu which I have heard described as a bull's horn was sometimes used as a sedile or seat, but I think, perhaps, as more of an added torture and humiliation than to provide any amount of comfort. "Messy" and no doubt an excruciatingly painful and lenthy way to meet one's demise, but that was the general idea, I imagine.
