This book's focus is on several advanced master keying topics, and is not intended for those not already familiar with proper master keying techniques. The skills covered should only be used by locksmiths who are well grounded in basic and intermediate master keying techniques, and fully comfortable with the Standard Progression Formula (SPF) charts and the development of standard master key systems using them. But if you are ready for the next level, including extensive coverage of incidental master keys and system threat handling, this is the book for you.