Homeowners have always been concerned about the security of their homes and possessions and have continued to improve locks in an effort to prevent unauthorized entry. Utilization of entry door locks with various types of keys enhanced security, but still left two problems to deal with. First was the problem of keyed locks being easy to get past the security feature. Keys were relatively easy to copy and locks could be picked. Second was the problem of lost or misappropriated keys.
Lock makers continued to improve the design of entry locks to make it more difficult to gain unauthorized entry. Security door locks added design features such as multiple automatic deadbolts which project further into the frame. Security door locks are affixed to the door with multiple independent security points. Extra pins or key faces make it more difficult to pick a security door lock. These improvements to security door locks provided additional security, but still did not solve the problems of lost or misappropriated keys.
Electronic door locks were the next step in the progression of security door locks. They rely on a plastic card with a magnetized strip on the reverse, similar to a credit card or other identification cards. An electronic door lock could also rely on bar code readers to open the doors. Again, the protection was enhanced by security door locks, so long as the card owner did not accidentally lose the card or have it stolen. Another problem with the electronic lock was losing the data stored on the magnetized strip for any one of several reasons. Some people consider card-type locks as keyless door locks.
Keyless door locks rely on other methods to enhance the security door locks and prevent the loss or theft of keys or cards. Often there is a number pad which requires keying in a sequence of numbers to release the security door locks mechanism. Keyless door locks often are linked to a home security monitoring system. Keyless door locks have the disadvantage of requiring the homeowner to remember the correct codes and being able to remember to use them. Most people will either write down the code and place it in an easily seen location; or will not use the security door locks at all.
Very high security door locks might include a fingerprint reader system, or ultimately a scan on the back of the eye which appears to be as unique as a fingerprint. These keyless door locks are almost impossible to circumvent. Although these keyless door locks are the most secure of the various types of security door locks, they are also the most expensive and will probably not be used by most people for residential applications. Keyless door locks of the latter type are commonly used in areas where unauthorized entrance is absolutely critical.