In the Middle Ages, nobles and people of the ruling class who were convicted of heresy, treason or other capital offenses were executed quickly. The object was a painless death. That was not true for the common people. For them, the longer the death process, the better the entertainment value for those inflicting punishment and those watching it occur.
Hanging was common. Not the kind of hanging we think about today (the "English drop") where the neck and spinal chord are quickly severed. Hanging where death could take several hours - or more. Hanging where the body is left to slowly strangle. Hanging where the victim is upside down, with a stone around his neck.
To inflict even greater punishment on the "convicted" heretic or criminal, authorities used "cat paws" to rip the victim's flesh to shreds. With hands unavailable to ward off flies and other insects, the accused would suffer even more as blood flowed from the shredded body.
In really heinous cases (like the story of William Wallace), the conscious victim would be taken down before death and disemboweled. In other cases, the victim's body would be racked with pain - before the hanging - by instruments of torture like the head crusher.