The Definitive Guide to Rotating Constant Master Keying RCMThis book is the definitive guide to one of the Locksmithing industry's least understood tools Rotating Constant Method of Master Key system design. Written in an easy to read language, it makes this previously often misunderstoodtechnique very clear. It covers many techniques generally unknown in the security industry. RCM, while quite simple once you fully understand it, is still considered an advanced technique. This book is your absolute best way