This 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 to learn it. This book includes techniques such as the 'Defined By' label, and RCM subsets such as the Limited Position Progression (LPP), Limited Rotating Constant (LRC), as well as "pure" RCM for five pin, six pin or seven pin cylinders or cores. Every Commercial or Institutional Lock Shop should have this valuable training and reference manual available. Heavily illustrated throughout with many sample systems.