What is a Chubbschloss (lever-tumbler / Zuhaltungsschloss), and why was it historically considered "unpickable"?
A Chubb lock uses multiple stacked levers (Zuhaltungen) that each have to be lifted to a precise height — too far is just as wrong as too little. Invented in 1818 by Jeremiah Chubb, it remained the gold standard for safe doors and bank vaults for over a century.
How it differs from a single-lever mortise lock:
| Single-lever | Chubb lever-tumbler |
|---|---|
| One Zuhaltung — has to be lifted enough | 4–6 Zuhaltungen at different heights — each must be lifted to exactly the right height |
| Picking = lift, then push the bolt | Picking = balance all levers simultaneously at exact heights |
The "anti-pick" feature — the detector lever:
Chubb's clever addition: if a picking attempt over-lifts any lever, a detector engages and locks the entire mechanism. Even the genuine key can't open it until reset. So a failed pick doesn't just not open the lock — it tells the owner someone tried.
Where you still see them today:
- High-end safes and bank vault doors
- British insurance-grade door locks (BS3621 standard requires lever-tumbler style)
- Mailbox locks in older European post systems
The 1851 challenge:
For decades Chubb advertised his lock as "unpickable" with a £100 prize for anyone who could open it. American locksmith Alfred Hobbs picked it at the 1851 Great Exhibition in London using a custom tool — the Hobbs'sche Öffnungshebel (Hobbs lever) is named after him.
Tip: "Unpickable" is a marketing word, never a technical one. Every lock has a time-to-open under attack; the question is just how long, with what tools, and what skill level. Modern security ratings (e.g., Swiss VdS, German EN 1303) quantify this in minutes.
Go deeper:
Lever tumbler lock — covers the Chubb detector lever that signals a picking attempt and Hobbs' "2-in-1" pick that defeated it.- Chubb detector lock — the dedicated page on the re-locking "detector" feature and the 1851 Great Exhibition challenge Hobbs won.