The term knob lock is often used to refer to either doorknobs that are equipped with an internal lock, or a device that fits over an existing doorknob and makes it impossible to turn the knob in any direction. In both cases, a knob lock helps to make homes, offices, and a wide range of commercial buildings protected from unauthorized entry. Knob locks can also help to prevent young children from harm, when installed properly.
In terms of the different types of locking knobs for doors, two types are commonly employed for entrances and exits to buildings of all types. One type is the key doorknob lock. This is a simple doorknob that includes an internal lock that is operated by inserting a key into the lock component. Turning the key makes it possible to lock and unlock the door, effectively limited access to the building to those who have keys that fit the lock. This is the oldest and most common form of knob lock in the world today.
Knob locks for internal use often utilize a design that is known as a twist lock. Rather than allowing for the insertion of a key, doorknob locks of this type rely on a smaller knob that is situated in the middle of the doorknob. The small knob is turned left or right to lock or unlock the door. Knobs of this type are often used for master bedrooms or bathrooms in private residences.
An electronic version of the knob lock is also gaining widespread usage. This type makes use of a card key that is inserted into a scanner. If the scanner recognizes the card key, it will trip the lock on the doorknob, making it possible to enter the space. Hotels and motels often make use of this approach to guest security, since it is a simple task to re-code the scanner after each guest checks out.
A knob lock can also be a simple device that fits easily over a doorknob. Usually constructed of metal, there are also security locks of this type made with high quality plastics and resins. Parents of young children sometimes find these types of knob locks to be helpful in preventing curious children from entering rooms where they are not allowed, while still allowing adults to move freely around the home. Landlords also make use of this type of knob lock when a tenant fails to pay the rent and is asked to leave the premises.