The medieval torture device we're looking at today was called the Judas cradle.
It is basically just a wooden triangle supported by three wooden legs, the victim would then be placed on top of it with the tip of it inserted in the vagina or anus. the purpose was to stretch the orifice it was inserted into, or impale. Sometimes the victim would have weights strapped to his or her legs so it would add to the pain. Notice how his legs have a piece of wood connecting them, this is for when the victim moves one leg, it automatically moves the other one, adding to the pain. Victims would sit on this for as long as hours to days.