A door is a hinged or otherwise movable barrier that allows ingress and egress into an “enclosure”. The opening in the wall can be referred to as a “portal”. A door’s essential and primary purpose is to provide security by controlling access to the portal (doorway). Conventionally, it is a panel that fits into the portal of a building, room, or vehicle. Doors are commonly made of a material suited to the task of which it is to perform.
The door may be moved in various ways (at angles away from the portal, by sliding on a plane parallel to the frame, by folding in angles on a parallel plane, or by spinning along an axis at the center of the frame) to allow or prevent ingress or egress. In most cases, a door’s interior matches its exterior side.
Doors often incorporate locking mechanisms to ensure that only some people can open them. Doors can have devices such as knockers or doorbells by which people outside can announce their presence and summon someone either to open the door for them or give permission to open and enter.
Doors may have aesthetic, symbolic, ritualistic purposes. To be given the key to a door can signify a change in status from outsider to insider. Doors and doorways frequently appear in literature and the arts with metaphorical or allegorical import as a portent of change.
All ancient doors were hung by pivots at the top and bottom of the hanging stile which worked in sockets in the lintel and sill, the latter being always in some hard stone such as basalt or granite. Those found at Nippur by Dr. Hilprecht dating from 2000 BC were in dolerite. The tenons of the gates at Balawat were sheathed with bronze (now in the British Museum).
