Locksmithing Fundamentals and Practical Skills
Core concepts
A candidate must be fluent in the vocabulary and mechanics of the pin tumbler cylinder, the warded lock, the lever lock, and the disc/dimple mechanisms that show up on the bench. Know the anatomy: shell, plug, bible, driver pins, key pins, springs, and the shear line. Understand how a key lifts each pin stack so the break between key pin and driver pin aligns at the shear line, and how binding order (the sequence in which pins bind under rotational tension) governs picking and impressioning.
Skills to demonstrate
Terminology matters: bitting, cuts, spacing, MACS (maximum adjacent cut specification), key blank identification via bow shape and warding, and decoding by eye or caliper. Be able to explain impressioning (reading marks on a blank under light tension), the difference between picking and raking, and why shimming a padlock works. Measurement discipline-using calipers, recording depths, and verifying with a functioning control key-is tested as practical judgment.
Traps
Questions often confuse driver pins (in the shell) with key pins (in the plug), or imply that a lock opens at the first pin that sets rather than when all stacks align. MACS violations are a classic trap: a cut that steps more than the allowed difference will cause the key to bind or the pin to over-lift. Watch for wording that swaps "warding" (the profile that admits the correct blank) with "bitting" (the cut depths).
Rule of thumb
For a five-pin cylinder, verify every cut against the control key and check MACS before cutting metal-measure twice, cut once. If two adjacent cuts differ by more than the specification allows, the key will not turn smoothly even if every individual depth is correct.