What is a special key?
A standard key is a short strip of metal, usually brass or steel about 5cm long with grooves scored down either side of it and one side specially cut to match the tumbler and pin settings in its given lock. Special keys can be defined as any keys that vary from this description. Examples of special keys include old fashioned skeleton keys, tubular keys, dimple keys, magnetic or electronic keys, Abloy keys, four-sided keys, double sided keys and Zeiss keys (among many others).
Most houses use standard keys, although special keys can be used to offer additional security against lockpicking.
How do special keys work?
These keys work much like any other key, in that the key is inserted in the lock and turned to engage the tumblers. What’s different is how the tumblers are engaged. Special keys may have numerous sets of pins, magnetic mechanisms to engage the lock, or any number of other non-standard technologies to help increase the lock's security.
Where are special keys used?
Although they're most commonly used on portable devices like car locks and bike locks, non-standard locks are becoming more and more common in front and rear doors as home owners grow more security conscious too. These locks are specifically designed to be tough enough to withstand repeated punishment, be highly pick and bump resistant and keep the potential copies of your keys to an absolute minimum.
What sorts of variations exist?
There are many different types of non-standard lock and key systems; some keys have two sets of teeth, others have a cylindrical shaft or differently shaped teeth that are rounded or straight instead of jagged. Many of these keys require certification or some sort of proof of house ownership before a locksmith is allowed to cut a copy, and will often bear a printed message saying 'Do not copy', or something to that effect.