The ancient Egyptians were the first to use a kind of keys to open a door. They had a lock that was made up of a wooden bolt that fitted into a slot. Movable wooden pins known as tumblers were fastened in the top of the slot. When the bolt slid into place, the wooden tumblers dropped into holes cut in the bolt. The bolt was held fast until the tumblers were lifted with a key.
The first key looked like a giant-sized toothbrush with pegs instead of bristles on one end. When the key was put in the slot, the page went under the tumblers. Raising the key forced the tumblers out of the bolt, which was then easily drawn back.
The Egyptian key could only be used on that side of the door where the bolt was placed. The Greeks discovered a way to slide back the bolt from the other side of the door.
The Romans later became the most skillful lock makers of the ancient world. They made a great improvement in the key. The pegs on the end of the Roman keys were cut in many different shapes. Now a thief had to make a key with pins not only in the right position and length but also in the right shape.