The Romans used two quite different methods which were never combined, and whose employment depended on what, apart from the victim's death, was desired as an additional bonus by the State. They might best be described as 'fast' and 'slow'. Although death was the ultimate objective of both methods, the 'slow' was designed to inflict hideous suffering as well, on any particularly offensive criminal such as anyone guilty of treason. These poor wretches took up to six days to expire. Fitting a horn or saddle to the upright so that it projected between the victim's legs at the crotch and supported his body weight, they then nailed his wrists to the crossbar and left him for shock, pain, humiliating nakedness, starvation, thirst and the mockery of passers-by to finish off.
With the 'fast' method, however, used when it was more a case of speed than the infliction of unbearable pain almost infinitely prolonged, the horn was replaced by a tiny platform on which the doomed man stood, preferably on the balls of his feet. Now, instead of the wrists being nailed they were bound to the crossbar by leather thongs. Except for the strain of standing in that fashion, shame at his nakedness and the knowledge that death was only a couple of hours away, he was in no great distress or pain. When it came time to kill him, the executioner resorted to the crucifragium, a club-like horror with which he broke the legs. Deprived of their support, the body sagged and the entire weight was thrown upon the thongs, which promptly proceeded to strangle the circulation. In about an hour, it has been reckoned, paralysis, suffocation and heart-failure brought the execution to a merciful end.
(The Jesus Scroll)