A door knob is a kind of handle used for closing and opening a door. It is part of home security and is one of the most important devices among the door hardware products. A doorknob is placed a few centimeters from the edge of the door. Depending on decorative style, local culture and owner preference, the position of the doorknob on the door varies. A doorknob is operated by a latching mechanism and is generally made of metals. Wooden door knobs are also used. Design, price and quality of a doorknob vary from model to model.

There are mainly four types of doorknobs: entrance, passage, privacy and dummy. Entrance sets have keyed cylinders, and they are mainly used for outside doors. Passage door knobs, also referred to as closet and hall knobs, are placed where a lock is not needed. Closet and pantry doors also use passage knob sets. For baths and bedrooms, privacy door knobs are used. Door knobs of this type are lockable, but they do not have a keyed cylinder. For convenience, a generic unlocking tool is provided. Dummy doorknobs are fixed knobs that are an excellent solution for closet doors. A latch mechanism is not needed for this set. It is generally used on the inactive door of a set of double doors and French-style closet doors.

With the growing number of door hardware manufacturers, an extensive collection of door knobs in different color and design are available in the market. Modern as well as conventional doorknobs are also available in the market. The price of a doorknob depends on its style, propose and the quality of the metal used. When purchasing doorknobs, a customer should look for features such as durability, convenience, service and warranty. Doorknob kits are available for repairing and replacing doorknobs.