Doorknob

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A basic modern doorknob with a latching mechanism on the left.

A doorknob is a device which enables a door 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 them directly onto the spindle, and then securing one or more retaining screws (set screws) through the knob perpendicular to the flat of the pie. 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. In some countries like Germany, doorknobs are completely unknown and levers are used on all doors.

Doorknobs can spread 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. [1] 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.

Entrance: These door knobs are typically used on exterior doors, and include keyed cylinders.
Privacy: Typically used on bed and bathrooms, while they are lockable (unlockable with a generic tool), they do not have keyed cylinders.
Passage: Also known as Hall or Closet, these knob sets do not lock and are used in hall or closet doors.
Dummy: Single knobs that mount through backs of doors with single screws. These types are used for ball catch doors or other applications where a latch mechanism is not needed, but the look of a door knob is desired.