Doorknob

A door handle is an attached object or mechanism used to manually open or close a door. In the United States, a door handle generally refers to any fixed or lever-operated door latch device. The term door knob or doorknob tends to refer to round operating mechanisms.

The traditional door knob has a bolt or spindle running through it that sits just above a cylinder, to which the spindle is connected. Turning the knob pulls the cylinder in the direction of the turn. The end of the cylinder is the "latch bolt" (more simply known as the "latch"), which protrudes into a space carved out of the door frame, and which prevents the door from being opened if the knob is not turned. A spring or similar mechanism causes the latch to return to its protruding state whenever the knob is not being turned. escutcheon plates are the keyhole covers, usually circular, through which keys pass to enter the lock body. If the door handles have a square or rectangular plate on which the handle is mounted this is called the backplate. The backplate can be plain (for use with latches), pierced for keyholes (for use with locks), or pierced and fitted with turn knobs and releases (for use with bathroom locks). The plate on the front edge of the lock where the latch bolt protrudes is called the faceplate.

Door handles can be and have been made out of a wide variety of materials. Just a few examples include brass, white porcelain, brown mineral, cut glass, wood, and Victorian bronze.

The location of the door handle along the horizontal axis on the door may vary between a few inches or 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 handle is called the backset.

The location of the door handle along the vertical axis on the door may vary between 34 to 48 inches (860 to 1,220 mm).

In Europe door levers are more common than the door knob, while in the US, door knobs are traditionally preferred over door levers. However door knobs can be difficult for the young and elderly to operate. For this reason, door handles in most American commercial and industrial buildings and in many households use a lever-operated handle, rather than a knob, as the lever does not require a tight grip. Levers are also beneficial on doors with narrow stile widths where the reduced backset leaves insufficient space to comfortably turn a door knob.

...
Wikipedia