Anything longer than 8 inches is usually bent across the surface of the leg. While short bending is done with just the hands, braced bending is used to add a little leverage. However, metal longer than a foot can be bent in many other ways which is covered in Long Bending.
By placing the object on the leg, with or without padding, you can press down to bow the object. From there you place the object between your legs and use your hands and wrists to torque the object to a complete bend with help from the legs pushing inwards. You can also complete a bend by placing the object at the hip and using your body with the hand to collapse it downwards.
Large nails such as the 12″ spike shown above, wrenches, hammers and other objects are all bent in this manner. As usual, the hands are usually the weak point but this is a full body movement.
Here, Chris Rider, bends a hammer not into a “U” but an “S” shape. Amazing!
This feat of strength is covered in depth in Dennis Rogers’ Odd Object Bending and Breaking DVD set.