The iron maiden, often styled after the Madonna or a favorite daughter, was more an instrument of execution than torture. The device either enclosed the victim within, as the one below, or embraced with the victim with her arms. In either case, the point was to skewer the victim.

In the version above, the floor inside opened up to drop the victim into a rack of knives for disposal after he expired within the maiden.

http://www.torture-museum.com/iron_maiden.htm