The oldest preserved door locks we have ever found belong to the ancient Egyptians and date back to at least 2000 B.C. It’s believed, but not proven, that they existed even earlier than that. What separates the Egyptian lock from later inventions is the fact that the whole thing was made out of wood, the key included. In fact, the basic idea for a lock—the pin tumbler—is still the most common type used today. There was one minor difference between their keys and ours though: Theirs were nearly a foot long, which made it much harder for would-be thieves to pick the locks.It’s believed that the Egyptians designed these complex locks as a way to guard valuable items or places of religious significance. A simple latch or bolt normally sufficed, but this new system enabled places to be cordoned off, making actual security guards unnecessary. Also, the door could only be locked (or unlocked) from the outside, and a bolt was used to do the actual locking.