The Protector lock (also called the "moveable lock") was an early 1850s lock design by renowned American locksmith Alfred Charles Hobbs, the first man to be able to pick the six-levered Chubb detector lock at the Crystal Palace Exhibition in the year 1851, which was created with the intent of being a lock that could not be picked.
Before Hobbs and his revolutionary lock designs, locks were opened by making a series of false keys, in a process that could take extremely long periods of time; if the series was not properly completed in the lock, and the combination not exactly correct, the lock could not be defeated. This design was accepted as quite unbreakable until Hobbs became the first to be able to pick them, by using very fine and careful manual dexterity; applying a certain level of pressure on the bolt while manipulating each lever, one at time, using a tiny pick inserted through the keyhole.
In an attempt to create a better locking system, Hobbs proceeded to patent the Protector lock, which, complex in design as it was, involved a transfer in pressure between the lock's internal bolt and tumbler mechanisms to a fixed pin. Hobbs claimed that his design was impossible to defeat and superior to the locks that were then in use, but, in 1854, one of Chubb's locksmiths was able to crack it, aided by the use of special tools.
The Protector Lock was distinct from Hobbs's other major lock design of the time, which he called the "American lock", and which slightly preceded the protector lock, in various ways; while the "American lock" was complicated to use, and expensive to purchase, with the added disadvantage of requiring a very big key, it did not differ greatly from the Protector lock so far as the security it offered, and the Protector lock was described as being much simpler to use. The one advantage that the American lock did have over the protector lock was its actual potential for greater security, if certain internal parts of the lock and key were rearranged in a particular way.
- Phillips, B. p.9
- The Mechanics' Magazine p.269
- Phillips, B. p.10