Soft, cuddly and charming… NOT. This wood and metal torturous beast that we all associate with the inquisitions, was a monster and drove more fear into the hearts of “accused” heretics all accross Spain than Satan himself ever could. Sure it caused a few victims to die of a heart attack from the mere thought of having to be put on it and stretched into jelly, thereby being a bit counter-productive, but hey, every torture device has its flaws.

The rack was used to pretty much torture the victim into a confession, especially good when used on the “accused by the neighbor” heretics to get that very fair deal of “GODS forgiveness and quicker death at the stake” in exchange for their confession and not being made jelly of before the burning.
Also, the confession will save the heretic from hearing the loud popping noises made by snapping cartilage, ligaments or bones (his that is), the screaming (his again) and after the muscles, tissues, etc. become squishy, the limbs ripping off completely.

also, The spread-eagled posture left no part of the body invulnerable from the application of other devices like hot irons or pincers, (luckily by that point, the hot irons would be a cake walk) or immune from the attention of those gathered to observe the torture.

One powerful method for putting pressure upon a prisoner was to merely force him to view someone else being subjected to the rack (I can see why).

from Wikipedia:

The rack is a term for certain physical punishment devices.

The rack consists of an oblong rectangular, usually wooden frame, slightly raised from the ground, with a roller at one, or both, ends, having at one end a fixed bar to which the legs were fastened, and at the other a movable bar to which the hands were tied. The victim’s feet are fastened to one roller, and the wrists are chained to the other.

As the interrogation progresses, a handle and ratchet attached to the top roller are used to very gradually stepwise increase the tension on the chains, which induces excruciating pain as the victim’s joints slowly dislocate. By means of pulleys and levers this latter could be rolled on its own axis, thus straining the ropes till the sufferers joints were dislocated.

Additionally, once muscle fibres have been stretched past a certain point they lose their ability to contract, thus victims who were released had ineffective muscles as well as problems arising from dislocation.

Because of its mechanically precise, graded operation, it was particularly suited for hard interrogation, as to extract a confession.

Indeed, a person stretched on the rack presented the ultimate spectacle of the body in pain. A victim would often be placed on the rack naked or nearly so, and their taut skin

would run with the sweat of their agonies.

The crazy thing is that the nuts of medeival times made our modern ones look almost humane… well, not really. But the Sudan Militia man on my left would probably draw the line before reaching what the Inquisitioners of old did for a confession.