Romans and Chinese independently developed the concept of the portable padlock. Padlocks were popular and widely used throughout the ages, as they were cheaper than door locks and could be used in multiple ways, for everything from cupboards and trunks to safes and jewelry boxes, which were secured with tiny “finger ring” keys.

In those days, keys were a means to flaunt wealth. If you had a key it meant you were someone with property worth protecting. Some of these keys, forged of bronze and iron, not only fit the lock but resembled the architecture of the doors they fit into. Collectors today may be able to find keys from ancient Rome or medieval Europe, but the metal will be corroded.

Wooden block locks became widespread in Europe during the Middle Ages—they were primarily used on the doors of churches and important buildings. Placed on the outside of the door, the hollow wooden stock contained an iron bolt that often used warded locks. These devices were opened and secured by keys that looked a lot like the keys we use today.

An antique key usually has three basic parts: The part you handle and turn is known as the “bow,” the tab that operates the lock is called the “bit,” and the two are connected by a “shank.” This basic key design, wherein the bit corresponds to the wards and lever in a lock, was deployed for more than 1,500 years, in spite of the fact that it does not provide very good security—such locks are easily picked.

Antique keys are commonly referred to as bit or barrel keys, the former having a solid shank and the latter being hollow. Many people mistakenly call all old keys “skeleton” keys. But a skeleton key is a specific type of bit or barrel key designed to pass the wards of many different locks. In other words, it is able to unlock more than one door.

Iron and bronze keys from around the Viking Era in the 8th and 9th centuries tend to have round or oval bows, with animal or openwork plant motifs. Keys were also used symbolically in Viking culture. For example, when a woman was married, she was gifted with a set of shimmering bronze keys to indicate her powerful status as a married woman. These keys were typically attached to the outside of her clothing, next to household tools such as a knife or pair of scissors.

The bows on 8th-to-10th-century keys are often shaped like religious symbols such as crosses, bishop’s miters, trefoils, and quatrefoils—during the Middle Ages, Europeans believed in the magic of keys and locks. In particular, iron was thought to have the power to ward off evil and demonic spirits that would try to get into homes and churches through keyholes and other openings. Many door fittings of the era featured wrought-iron dragon heads meant to repel such spirits. Blacksmiths who worked with iron were revered and always positioned two pairs of tongs into a cross when they left their forge to protect their sacred craft.

Keys, too, were believed to possess great power. Superstition said that keys should never be put on a the table, as it led to chaos and disagreement in the house. In Finland, it was believed that keys in the bed would help a woman in the process of childbirth, while keys in the shape of crosses were thought to help cure boils.

Around Europe, church keys—usually tremendously weighty iron keys with a cross on the bit or bow—were considered particularly powerful, able to cure whooping cough and calm unruly children. And early medieval church art depicts Saint Peter being handed the key to the kingdom of Heaven.

Up until the 18th century, the keys to a city’s gates were tangible symbols of a municipality’s independence. When a city would surrender to an invading army, it would turn over its keys.

While key design had been a source of pride for master craftsmen for ages, it wasn’t until the 16th century that keys became more extravagant than utilitarian. The introduction of the flamboyant and frilly baroque and rococo styles in France required the employment of the most talented craftsmen for every detail of the palaces, right down to the door knobs, door plates, locks, and keys.

The French Locksmiths’ Guild set a high standard for beautifully and intricately designed keys and locks. The English locksmiths of the time made locks that were just as technically proficient, but they rarely bothered to put such ornate decoration on them.

During the late 18th and early 19th centuries, the English were much more interested in making locks that were difficult to pick, employing complicated lever systems like Robert Barron’s 1778 double-acting tumbler lock and Jeremiah Chubb’s 1818 lock. In 1784, Joseph Bramah patented his safety lock, which was opened by a cylindrical key with slides that must be exactly the right length to turn the bolt.

Then, in 1848, the American Linus Yale and his son invented the cylinder lock, also known as the modern pin-tumbler lock, which is still commonly used today. The key has a blade instead of a shank, and the blade is cut with horizontal grooves that allow the key to be inserted past the wards in the cylinder. When the key is turned, the “bittings” carved along the bottom of the blade operate the pins or wafers inside the lock, allowing the cylinder to turn freely.

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