Because they are such a common sight, we often take the lowly door knob for granted. Actually, a door knob is a special type of door handle which is used for opening and closing a door. Because of its round shape, it is termed instead as a “knob”.
Developed as early as the 18th century, door knobs have a central cylinder to which a bolt or spindle is connected via a mechanism of springs and tumblers. Turning the knob causes the cylinder to turn along with it. Depending upon the direction of the turn, the spindle protrudes into a notch on the door frame or retracts, thus closing and opening the door respectively. Door knobs have a button which, when pushed, prevents the spindle from retracting, causing the door to be locked. A key pushes the tumblers inside the knob to release the button, enabling one to open the door.
Door knobs come in many styles. While most are simply utilitarian in design, some door knobs have ornate hand grips that match wood-carved doors. Leading door knob manufacturers include Schlage, Kwikset, Emtek and Sure-Loc.
Before, one has to go to a hardware shop to buy a door knob. Thanks to the convenience of the Internet, a wide variety of door knobs and other door handles can be purchased from online hardware shops. Check out their catalogs for the door knobs that best match the design of the door and also provide home safety.