A door knob is a type of door handle that is round in shape - distinguishing it from a door lever. Door knobs open and close a door when they are twisted in either direction. Door knobs, especially those used on exterior doors, often incorporate a lock, usually located in the centre of the knob. An escutcheon plate may also be attached to the door behind the door knob to give it some clearance from the door itself.
How do door knobs work?
The knob is connected to a spindle (i.e. a long piece of metal), square in shape, which twists when turned and engages the cylinder which withdraws the latch bolt that holds the door closed. With the latch bolt withdrawn into the door, the door can open freely. A spring returns the latch bolt to its protruding state when the door knob is released, which prevents the door from opening again until you twist the door knob again.
Where are door knobs used?
Door knobs are very commonly used throughout the house on both interior and exterior doors. The decision to use these over a lever mechanism largely comes down to aesthetic appeal, although people with arthritis or other fine motor or hand impairments may find it easier to operate lever handles than doorknobs.
Door knobs in homes use different types of locks - in most Australian homes, it's uncommon to see keyed locks used anywhere but on the front door. Door knobs used for bedrooms, bathrooms and toilets often use simple privacy locks (sometimes referred to as 'privacy snibs'), allowing the door to be locked from one side for a bit of privacy.
How should door knobs be installed?
In Australia, door knobs are typically located a few centimetres away from the edge of the door to the left or right side, depending on handing and swing direction. This makes it important to be careful when opening the door, so as to prevent the knob from smashing into a wall. This can be especially disastrous with plaster walls, where a decently swung door can leave holes. In most cases, this is prevented using a door stopper.
Some door knobs are located in the middle of the door, though this is more of an English tradition and is quite rare these days.
How high should door knobs be?
The Australian Standard AS 1428.1 (Design for access and mobility, Part 1: General requirements for access) recommends that door handles of all types should be installed at a height not less than 900mm and not more than 1100mm above the plane of the finished floor. Most door knobs are installed at around this height (i.e. around waist height for the average adult), although in some older houses door knobs or levers are installed much higher up.
Are there any variations?
Apart from the various materials and sizes available, many door knobs - especially on front entranceways - are ornamentally decorated and can be fashioned into many shapes, such as a lion’s head or a fist. Elaborate, ornamental door knobs are typically quite a bit pricier than standard door knobs but can make a nice visual impact if they're used appropriately.
Door knobs are generally supplied with the locking mechanism already attached - either as a key in knob setup for external doors, or knobs with privacy locks incorporated into them for bathrooms and bedrooms.
