A: In the video, we talk about hammering the coils after they're created in order to keep their shape. This method is termed "work hardening". When the rawhide hammer hits the metal, it causes the metal to then harden in that shape it's been placed into (as an alternative, when the metal is heated up, it can become soft again or "annealed"). A rawhide hammer will cause the metal to harden without changing the shape of the wire when it's struck - very important! If you were to use a metal hammer (e.g. ball peen) the metal will misshapen. Answer provided by:  JewelrySupply (1/15/2018)