This book describes a firearm lock designing process, developed by Master Gunsmith and Master Bladesmith, Steve Culver. Steve developed this method for use in his own shop, to facilitate the designing of flint-locks and percussion locks for the guns that he builds. The information in this book, shows how to design a firearm lock that includes a half cock notch. How to design a fly in a tumbler. Plus other design considerations and choices that must be made during the designing of a firearm lock.