Types of door
Many kinds of doors have specific names, depending on their purpose. The most common variety of door consists of a single rigid panel that fills the doorway, hinged along one side so that it can fold away from the doorway in one direction but not in the other. Many variations on this basic design are possible, such as "double" doors that have two adjacent independent panels hinged on each side of the doorway.
A trapdoor is a door that is oriented horizontally in a floor or ceiling, often accessed via a ladder.
A stable door is divided in half horizontally. The top half can be opened to allow the horse to be fed, while the bottom half can be closed to keep the animal inside.
A swing door has special hinges that allow it to open either outwards or inwards, and is usually sprung to keep it closed. Saloon doors are a pair of lightweight swing doors often found in public bars.
An up-and-over door is often used in garages. Instead of hinges it has a mechanism, often counterbalanced or sprung, that allows it to be lifted so that it rests horizontally above the opening.
A barn door is a very large sliding door that covers the entire side of a barn.
A French door is a door that has multiple lights, the full length of the door. Traditional French doors are assembled from individiual small pieces of glass and mullions. French doors made of double-pane glass (on exterior doors for insulation reasons) may have the decorative grill embedded between the panes. The decorative grill may also be superimposed on top of single pane of glass in the door.
A sliding glass door is a glass door that slides to open. It goes in an opening at least twice the width of the sliding door and is composed of two panels of glass. One panel is fixed and the other slides. Sliding glass doors are most commonly used for large views of backyards
A garden door is any door that opens to a garden or backyard. It is often used specifically for double French doors in place of a sliding glass door. In such a configuration, it has the advantage of a very large opening for moving large objects in and out.
A pet door is a opening in a door to allow pets to enter and exit without the main door being opened. It may be simply covered by a rubber flap or it may be an actual door hinged on the top that the pet can push through. Pet doors may be mounted in a sliding glass door as a new (permanent or temporary) panel. Pet doors may be unidirectional, only allowing pets to exit. Pet doors may be electronic, only allowing pets with a special electronic tag to enter.
Door construction
Traditional doors are constructed from vertical planks of wood held together by horizontal beams called ledges (hence ledged door). Often they are strengthened by diagonal beams, running upwards from the hinges, called braces (hence braced and ledged and braced doors).
Recently (c. 20th century) hollow doors have been used, consisting of a thin wooden frame covered by hardboard or plywood. Many houses now have external doors that are aluminium-framed with a polyvinyl chloride exterior. Steel doors are also very common for exterior doors.
Doors are constructed to be symmetric. Which way it opens is determined at installation when the hole for the door knob and lock and bolt are drilled on-site to match existing lock locations. For hollow doors, the area where the door knob goes is not hollow but solid and reinforced.
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