Once the hollow section has been opened, the wall is flattened while still hot by being pressed down with the foot (figure IV.7) or tapped with a wooden mallet. Flattening is completed by placing the horn, while still hot, in a wooden vice and/or tapping it with a wooden mallet.

If the hollow section is to be flattened for the manufacture of buttons, spoons, and so on, whose width is less than half the circumference of the hollow section, the horn should be cut as indicated in figure IV.8. It will then be easy to flatten the two hollow section halves by heating them and gripping them tightly between the jaws of a wooden vice.