We all know what a padlock is, padlocks are portable locks designed to provide security for moveable items or things stored in temporary or unlocked building - like a shed. The idea of padlocks has been around for centuries and according to Wikipedia, the first one was made way back in the 17th century. Undoubtedly it was large, heavy and expensive. Later on English locksmiths built very large padlocks which they challenged all comers to "pick", just to prove how strong and sturdy their portable locks were.
The padlocks we have today have evolved a long way from those big heavy forebears. The first of what we think of as modern padlocks made their appearance in the early 20th century when a patent was granted to the Master Lock company for their design of a small and inexpensive but portable lock made from layers of steel (similar to the door of a bank vault).
Nowadays, padlocks are available in a wide range of designs, sizes and materials, but their purpose remains the same - provide simple, easy to use portable security. All padlocks do this by combining two component parts, a shackle that can be opened and closed and a locking mechanism (either a combination or keyed) to secure the shackle in place.
Today's steel padlocks are commonly made from alloyed steel for strength and usually capable of resisting brute force to open them. For outdoor work where they'll be exposed to the elements, the steel can covered with a plastic coating to prevent rusting as well as being color coded or coordinated. Padlocks can be made from other metals, for example brass, and while a brass lock will be attractive and resist rusting the metal is softer than steel so can't provide the same amount of security as a steel lock.
The most common locking mechanism for a padlock is the familiar combination lock, often used for school and gym lockers. Turning the dial through the proper sequence of numbers aligns the tumblers inside the lock and releases the grip on the shackle. Other commonly available combination locks, such as the padlock with a number pad on the side of the locking mechanism - are often used for locking bicycles or even securing computers to a desk.
The majority of combination locks have a single combination that's pre set by the manufacturer. However, more expensive padlocks that allow you to set your own combination (and change it when you want to) are also readily available.
Keyed padlocks have the same basic structure as combination locks but with the obvious difference that the locking mechanism is controlled by a key inserted into a keyhole - usually in the lock's base. The main downside to keyed padlocks is if the key is lost, the lock can't be opened and it can only be removed by cutting through the shackle. (That's why they give you two keys with all new padlocks).
Maintaining a Padlock
Padlocks in general are pretty low maintenance, even padlocks that are used outside don't require much. However, over time dust and weather can get into the lock and make the locking mechanism stiff, so some quick annual maintenance will keep your lock working properly.
A blast of compressed air from a can (available at a computer or electronics store) or if you have one, a home compressor will blow any dust out of the lock. Then all you need to do is lubricate the locking mechanism with a quick squirt of lock lubricant - a "dry" graphite based lubricant specially formulated for locks. Never use household or machine oil in a lock, this will actually hold dust inside the lock and over time make the mechanism extremely stiff.
While modern padlocks themselves work well, overall security depends on how and where they're used. Commonly a padlock is out in the open and looped through a hasp secured with short screws. A quick jerk with a pry bar of even a blow with a sledgehammer is often enough to pull the screws securing the hasp right out of the wall, allowing the locked door to open even though the padlock itself is still locked.
No matter how good it is, a padlock isn't a total solution, it can only be part of an overall security plan.