The term boot refers to a family of instruments of torture and interrogation variously designed to cause crushing injuries to the foot and/or leg. The boot has taken many forms in various places and times. Common varieties include the Spanish boot (sometimes referred to as "scarpines") and the Malay boot. One type was made of four pieces of narrow wooden board nailed together. The boards were measured to fit the victim's leg. Once the leg was enclosed, wedges would be hammered between the boards, creating pressure. The pressure would be increased until the victim confessed or lost consciousness. Newer variants have included iron vises—sometimes armed with spikes—that squeezed feet and metal frames employed red-hot.
The Spanish boot was an iron casing for the leg and foot. Wood or iron wedges were hammered in between the casing and the victim's flesh. A similar device, commonly referred to as a shin crusher, squeezed the calf between two curved iron plates, studded with spikes, teeth, and knobs, to fracture the tibia and fibula.
Primitive forerunners of the archetype can be found dating back as far as a thousand years. The first Scottish effort, also referred to as a buskin, made use of a vaguely boot-shaped rawhide garment that was soaked with water, drawn over the foot and lower leg, and bound in place with cords. The contraption was slowly heated over a gentle fire, drastically contracting the rawhide and squeezing the foot until the bones were dislocated, though there would not have been sufficient pressure actually to crush the bones of the foot. A more progressive variant, found in both the British Isles and France, consisted of a trio of upright wooden boards that splinted around and between the feet and were tied in place by cords. Wedges were hammered between the boards and the feet to dislocate and crush the bones. A prototype hailing from Autun, France, consisted of high boots of spongy, porous leather that were drawn over the feet and legs. Boiling water was poured over the boots, eventually soaking through the leather and eating the flesh away from the entrapped limbs. Lastly, oversized boots of iron or copper (often soldered in place on the floor) received the prisoner's bare feet as he lay helplessly bound and gagged in a chair. The boots were slowly filled with boiling water or oil, or even molten lead, to consume the feet and legs. One variant—applied in Ireland to the martyr Dermot O'Hurley—consisted of lightweight metal boots that were filled with cool water and heated with the feet inside over a fire until the water boiled aggressively.