The History and Design of the Lock and Key

For millennia, the structure of the mechanical lock has been incorporated into different aspects of society. Some locks are in place to keep our possessions safe, others to protect us from dangerous people or objects. However, the design, complexity and strength of locks and keys have altered significantly over time.

The first known locks in history were created over 6000 years ago in Ancient Egypt and Mesopotamia. These simple yet effective mechanisms were called pin-tumbler locks and were made entirely from wood. The lock consisted of a wooden post fixed to the door and a large wooden bolt, which secured the door in place, with a set of holes in its upper surface. Attached to the door would have been an assembly of wooden pins, specially positioned to drop into the holes on the bolt. The key was a large wooden bar, shaped like a toothbrush, with upright pegs that corresponded to the holes and pins in the lock. When inserted into the large keyhole below the vertical pins, the key was simply lifted, raising the pins clear and allowing the bolt to be moved. One of the oldest examples of a pin-tumbler lock was found in the ruins of the palace of Khorsabad near Mosul in Iraq.

During the first millennium bc the Greeks introduced better designs for their locks. The bolt for these locks was moved by a sickle-shaped key made of iron. The key was passed through a hole in the door and turned so that the point of the sickle engaged the bolt and drew it back. However, these locks were very insecure, so the Romans, trying to improve upon Greek and Egyptian locks, introduced metals for their locks, making them mainly from iron. They also invented wards – projections around the keyhole, inside the lock – which ensured that only the correct key with slots on it corresponding to the projections could rotate and move the bolt. These keys were also much smaller than that of the pin-tumbler locks and could be worn in pockets, or as a pendant or ring. For centuries, locks depended on these wards to make them secure. However, they were relatively easy to pick compared with more modern locks.

After the fall of the Roman Empire in the first century ad, innovation of locks halted. Locksmiths in the European Dark Ages had neither the technology nor the funds to invent new locks, but instead used their time to create new ways to confuse lock pickers by designing multiple key mechanisms, increasingly complicated key designs and fake and obscured keyholes.

In the Middle Ages, a large number of workmen were employed in making metal locks: the German metalworkers of Nuremberg are prominent examples. The moving parts of the locks they made were closely fitted and the exteriors were lavishly decorated. Despite their improved appearance, the security of the locks was still dependent on elaborate warding as the mechanism of the lock had hardly been developed at all. The first major improvement on the ancient Roman warded lock was made in 1778 when Robert Barron created a double-acting tumbler lock. Tumbler locks use a lever that falls into a slot in the bolt of the lock, which prevents it from being moved until the lever is raised by the key to exactly the right height out of the slot, so you can then slide the bolt out. The Barron lock had two tumblers and the key had to raise each of the tumblers by a different amount before the bolt could be moved. From this and the ground-breaking developments of Joseph Bramah, Jeremiah Chubb, Linus Yale Sr., James Sargant, Samuel Segal and Harry Soref, the modern locks that we use to date were designed and manufactured.

Two of the names from that list of locksmiths are well known around the world today as the majority of houses in the developed world will have Chubb or Yale locks, named after Jeremiah Chubb and Linus Yale Sr., securing their doors. Not only did Linus Yale Sr. invent the modern Yale pin-tumbler lock in 1848, he and his son also introduced the modern flat key to the public in 1861. Today the majority of the world uses these flat keys to activate their modernised pin-tumbler locks.

If we were not currently in the midst of the pandemic and could go about our daily lives as normal, we would still be using locks to lock up our shops, lock up our possessions and lock our doors. However, these are not normal times. Currently, we are in a national lockdown, locked in our houses and separated from the rest

of society. The symbolism of the lockdown could be interpreted in two ways: either the government trying to protect citizens by locking us up to keep us safe; or locking us up to keep the dangerous people, possibly the infected, away from the rest of society. Depending on how you interpret it, we are either prized possessions or prisoners trapped behind the locks.

Drawing by Isabelle Guthrie (DA Sh)