Dating back to ancient China and Rome, the warded lock is one of the oldest lock designs. The principle of the lock is that it uses a set of obstructions, or ‘wards’, which prevent the lock from opening unless the correct key is inserted.
Due to the design of the warded lock a skeleton key can easily be made to bypass the wards. There are also a limited number of unique keys that can be created, so keys will be able to open other locks for which they were not designed to.
For these reasons warded locks are mainly used for low-security purposes.
Lever Tumbler Lock
Invented by Robert Barron of England in 1778, the lever tumbler lock as its name suggests uses a set of levers to prevent the bolt from moving in the lock. In the most simplest of forms the levers only need to be lifted above a certain height to allow the bolt to slide past.
The number of levers, which are usually made out of non-ferrous metals, vary from lock to lock but are usually an odd number. This is to allow the lock to be opened from each side to provide symmetry.
3 lever locks are typically found in internal doors as they are less secure whilst 5 lever locks are widely recognised as being a secure lock and are often required for home insurance.
Pin Tumbler Lock
The pin tumbler lock dates as far back as 4000 BC in Egypt and is actually one of the most common types of locks used today.
The lock uses a set of pins to prevent it from being opened unless the correct key is used. When the correct key is inserted into the lock, the series of pointed teeth along the blade of the key called bittings allow the pins to move up and down. When the pins are inline with the shear line of the inner and outer cylinders of the lock the cylinder can then freely rotate and allow the lock to open.
Wafer Tumbler Lock
A wafer tumbler lock works on a similar principle to that of the pin tumbler lock. The main difference between the two is where the pins in the pin tumbler lock are in multiple pieces the wafers in the wafer lock are a single piece.
Manufactured to low tolerances most wafer tumbler locks can be opened very easily by keys of a similar pattern. They are most commonly used in office furniture, lockers and electrical panels.
Disc Tumbler Lock
Not to be confused with the wafer tumbler lock, the disc tumbler lock is composed of slotted rotating discs.
Invented by Emil Henriksson in 1907 the disc tumbler lock uses a specially cut key that rotates the rotating discs like the tumblers in a safe to align the slots and therefore allowing the lock to open. Unlike other types of tumbler lock, disc tumbler lock mechanisms do not use springs meaning they are suitable for outdoor and harsh conditions.
Disc tumbler locks are often more difficult to pick than other types of locks, although not impossible with professionally-made tools. For this reason they are often sold as “high security” locks.