A doorknob is a device which enables a door as well as a cabinet to be opened. Most household doorknobs use a simple mechanism with a screw-style axle (called a spindle) that has at least one flat side, which is passed through the door latch, leaving some length exposed on each side of the door to which the knobs are attached. Knobs are attached on both sides by screwing or sliding them directly onto the spindle, and then securing one or more retaining screws (set screws) through the knob perpendicular to the flat of the spindle. Doorknobs that lose traction can frequently be repaired by replacing or adjusting the set screw, which prevents them from slipping on the spindle.
The location of the doorknob on the door may vary between a few centimeters away from the edge of the door to the exact center of the door, depending on local culture, decorative style or owner preference. The distance from the edge of the door to the center of the doorknob is called the backset.
Doorknobs can be difficult for the young and elderly to operate, especially infants. If a person lacks a firm grip a doorknob must sometimes be operated using two hands. For this reason doors in most commercial and industrial buildings and in many households now use an operating lever, rather than a doorknob, as the lever does not require a firm grip. Levers are also beneficial on doors with narrow stile widths where the reduced backset leaves insufficient space to comfortably turn a doorknob.
Of nearly universal concern is the thought that doorknobs are instrumental in the spread of many infections. Some materials, e.g. brass, copper and silver, are poisonous to many germs, via the oligodynamic effect. Brass and copper, for example, disinfect themselves of many germs within eight hours. Other materials such as glass, porcelain, stainless steel and aluminum do not have this effect. Self-disinfecting doorknobs are particularly important in hospitals, but useful in any building.
A doorhandle is the device mounted on the exterior and interior of a door for the purpose of opening it.
In the US, the word doorhandle is mostly restricted to car doors because on other doors, doorknobs are more common. Car doorhandles might portrude from the vehicle's exterior surface or be streamlined into the vehicle's contour. In some automobiles, especially luxury vehicles, the doorhandles might be decorated with chrome and feature a keyless entry pad utilizing either a numerical code or thumb scan.
In the UK doorhandles and doorknobs are two separate things. A knob is rounded whereas a handle is long and slim.