Locks are something you use every day, whether at your apartment, home, car, or work: but how do they actually work?
Today, you’ll get to learn from a professional locksmith how a lock works and what happens every time you put your key in and turn.
How does a “keyed” lock work?
To better understand the scope and function of our work as locksmiths, we thought it may be helpful to provide a more detailed and somewhat technical reflection on the question, “how does a keyed lock work?” (We specify here “keyed” lock to distinguish from others locks that may require a code or combination.)
With many modern locks, whether for a vehicle, pad lock or house lock, not much has fundamentally changed since their inception. What has changed is some of the added technology (see our blog post on smart locks, some of the newest and best technology in home security, here).
A typical keyed locked refers to a “pin” or “tumbler” lock which uses a series of pin stacks organized to prevent the rotation of an inner cylinder core unless the precise/correct key is inserted.
Let’s go over the key component to better grasp how the basic mechanism works:
- PLUG (cylinder core) — The rotatable inner cylinder containing the keyway (slot for the key).
- SHELL (case cylinder housing) — The fixed outer body that encases the plug.
- PIN STACKS — Typically 5–6 vertical chambers (bores) aligned between the plug and shell. Each stack consists of:
- Bottom Pins: Rests in the plug and actually contacts the key.
- Top Pins: Sit above the key pin in the shell, pushed downward by a spring.
- Springs: One per stack, applying downward pressure on the driver pins.
- Shear line: The precise line (gap) between the plug and the shell.
- Bible: The upper part of the shell housing the necessary pins and springs.
Here are some diagrams* to illustrate (in part) the basic operation:
Without a key in the lock, the top pins (blue) are pushed downwards, preventing the plug (yellow) from rotating.
With the correct key in the lock, the top pins (blue) and the bottom pins (red) begin to align at the shear line allowing the core to rotate freely (thus, unlocked).
With a wrong key, the bitting (cuts on the key blade) lift the key pins to incorrect heights and will still cross the shear line, thus blocking rotation, see below.
How does all of this relate to our locksmith work and your possible lock needs? Our mobile technicians can come out to your location to provide these type service:
- Pick and decode the lock in order to generate a working key
- Re-key and match keys to a new keyway to provide safety – which in most cases we can do without replacing the locks or hardware on your doors.
- Repair and replace broken hardware
*Photo/Diagram credit – Eric Pierce gmail wapcaplet88, available also at wikipedia
**Historical side-note: The modern pin/tumbler lock mechanism was refined in the mid-19th century by Linus Yale (which is reflected in a very popular name brand manufacturer of locks to this day).