How did the Romans change the materials used for locks and keys?

The Romans significantly advanced lock technology by transitioning from the wooden materials common in earlier civilizations to the use of metals. They typically utilized iron for the construction of the lock itself, while keys were frequently crafted from bronze.1

Because bronze keys were more durable than their iron counterparts, they are discovered more often in the archaeological record today than the locks they operated. This shift to metal allowed the Romans to innovate in design, enabling them to create the first small keys—some of which were compact enough to be worn as rings—and to invent the padlock. Additionally, the Romans introduced wards, which are internal projections that require a key to have specific slots cut into its bit to rotate, further enhancing the security of their metal-based locking systems.1