Lock Types + Mechanisms Reference

Overview

Understanding how locks work is foundational to locksmithing. This reference covers the common residential lock mechanisms + how each operates.

Pin tumbler lock (most common)

The standard residential lock. Same mechanism in 90% of homes.

Components:

• Plug (rotating core): holds keyway, rotates when correct key inserted
• Cylinder housing (stationary): contains pin chambers
• Pin chambers (5-6 typically): contain key pins + driver pins + springs
• Key pins (bottom): different lengths, each at a pin position
• Driver pins (top): typically standard size, prevent plug rotation
• Springs: push driver pins down into plug
• Shear line: boundary between plug + cylinder; pins must align here

Operation:

1. Key inserted: pin tips push key pins up
2. Correct key positions key pins so the gap between key + driver pin is at the shear line
3. Plug rotates freely (no pin obstructing)
4. Wrong key: pins misaligned, plug blocked

Bumping: specially-cut "bump key" inserted, hammered while turning; bounces driver pins above shear line momentarily; plug turns.

Picking: tension wrench applies torque; pick lifts each pin to shear line individually.

Wafer tumbler lock

Simpler than pin tumbler. Common in older residential, locker keys, file cabinets, some automotive.

Components:

• Wafers (flat metal plates with rectangular slot)
• Springs pushing wafers downward
• Key engages wafers, aligns slots at center axis

Operation: correct key aligns all wafer slots; plug rotates.

Security: lower than pin tumbler; easier to pick + bump.

Disc detainer lock

Mid-security; used in some Abloy + Medeco models. Sometimes seen on padlocks + commercial.

Components:

• Rotating discs (not pins)
• Disc has notches at specific angle
• Sidebar blocks rotation until all discs aligned

Operation: key rotates each disc to correct angle; sidebar drops into aligned notches; plug rotates.

Security: higher than pin tumbler; bump-resistant; specialty picking required.

Tubular lock

Found on some vending machines, gun safes, bicycle locks.

Components:

• Cylindrical key with pins around circumference
• Multiple pin chambers radially arranged

Operation: like pin tumbler but circular.

Security: susceptible to specialized tubular pick tools.

Combination lock

No key; rotated dial(s) align internal mechanism.

Types:

• Single-dial combination: dial rotates through multiple combinations
• Multi-dial (e.g., briefcase locks): 3-4 dials with numbers
• Electronic combination: digital, often battery-powered

Operation: correct sequence of rotations + numbers aligns internal mechanism; opens.

Lever lock

Older mechanism, mostly UK/Europe. Some legacy US.

Components: spring-loaded levers, must all be lifted to correct height by key bittings.

Operation: correct key lifts each lever to align bypass slot; bolt withdraws.

Security: old technology; varies widely.

High-security locks

Specialty mechanisms with sidebar locks, restricted keys, anti-pick + anti-bump.

Manufacturers:

• Medeco: angled pins + sidebar
• Mul-T-Lock: telescoping pin-in-pin
• Abloy: disc detainer + sidebar
• BiLock: dual sidebar mechanism

Security: highest mechanical security; resistant to most attacks; restricted key blanks (only licensed locksmiths can duplicate).

Cost:.

Electronic / smart locks

Modern category, growing fast.

Categories:

• Keypad: code entry
• Bluetooth: smartphone proximity
• WiFi: remote control via internet
• Z-Wave / Zigbee: home automation hub
• Biometric: fingerprint, retina

Components:

• Electronic actuator (motor)
• Mechanical override (typically a keyway as backup)
• Battery (typically AA, 6-12 month life)
• Optional: WiFi module, hub connectivity

Security considerations:

• Battery dies → mechanical override or emergency power
• WiFi hack risk → use reputable brand
• Code privacy → don't share with everyone
• Compatible with smart home (HomeKit, Google, Alexa)

Mortise lock

Pocket cut into door edge; lock body fits into pocket.

Common in: older homes, commercial, high-end residential.

Advantages: strong, full-function (deadbolt + latch in one unit), traditional appearance.

Disadvantages: requires significant door modification, expensive, less common products.

Cam lock

Tube + cam; turns 90° to lock/unlock.

Common in: cabinets, drawers, lockers, mailboxes.

Operation: key rotates cam; cam engages strike.

Padlock

Portable shackle lock.

Mechanisms:

• Pin tumbler (most common)
• Wafer (lower security)
• Disc detainer (mid-security)
• Combination

Components: shackle (U-shaped bar), body, key mechanism.

Strike plate (not a lock, but critical)

Metal plate on door frame that receives the bolt.

Quality matters:

• Cheap strike: 2 screws, kickable
• Standard: 4 screws, mid-security
• Security strike: 6+ screws, extended into stud, much harder to kick

3-inch screws are non-negotiable for security; 1-inch screws (factory-included) pull out.

Specialty locks

Cylindrical lockset: combined knob + lock (basic residential)

Tubular deadbolt: dedicated deadbolt (high-security recommended)

Multi-point lock: multiple bolts at top, middle, bottom (high-end residential, commercial)

Mortise deadbolt: full mortise installation; serious security

Knob over deadbolt: most residential exterior doors

Lever lockset: ADA-compliant; lever vs knob

Privacy lock (bathroom): no key from outside; emergency unlock via small hole

Lock grading

ANSI / BHMA grades indicate quality + durability:

Higher grade = more durable + costlier.

For exterior doors: Grade 2 minimum recommended. For interior: Grade 3 fine.

Re-keyable locks

Some modern locks rekey without disassembly (e.g., Kwikset SmartKey):

• Insert old key + turn
• Insert special tool
• Remove old key
• Insert new key + turn
• Lock now responds to new key only

Trade-off: faster rekey but slightly lower security than traditional pin tumbler.

Common residential brands

• Kwikset: budget-mid; SmartKey re-keyable; widely available
• Schlage: mid-premium; very common; durable; restricted key option (Primus)
• Yale: mid-premium; smart locks common
• Master Lock: padlocks, basic residential
• Medeco: high-security
• Mul-T-Lock: high-security
• Abloy: high-security

How locks fail

• Internal wear: pins + springs over years (5,000+ uses)
• Dirt + grit: especially exterior locks
• Frozen (cold climates): water freezes inside
• Bent key: key tip breaks off inside
• Damaged keyway: bent or chipped
• Spring failure: pins don't return; key sticks
• Cylinder retention failure: cylinder loose in door

References

• ANSI/BHMA A156 lock standards
• ALOA mechanism training
• Manuall internal: Rekey + Lock Change SOP, Install a Deadbolt