Interior Construction. Doors.

A door is a panel or barrier, usually hinged, sliding, or electronic, that is used to cover an opening in a wall or partition going into a building or space. A door can be opened to give access and closed more or less securely. The term door is also applied to the opening itself, more properly known as the doorway.

Doors are nearly universal in buildings of all kinds, allowing passage between the inside and outside, and between internal rooms. When open, they admit ventilation and light.

The purpose of a door closure is primarily to give occupants of a space privacy and security by regulating access. For this purpose doors are equipped with a variety of fittings ranging from simple latches to locks.

The door is used to control the physical atmosphere within a space by enclosing it, excluding air drafts, so that interiors may be more effectively heated or cooled. Doors are significant in preventing the spread of fire.

Doors also have an aesthetic role in creating an impression of what lies beyond. They are also used to screen areas of a building for aesthetic purposes, keeping formal and utility areas separate. They act as a barrier to noise.

Doors are often symbolically endowed with ritual purposes, and the guarding or receiving of the keys to a door, or being granted access to a door can have special significance. Similarly, doors and doorways frequently appear in metaphorical or allegorical situations, literature and the arts, often as a portent of change.

When framed in wood for snug fitting of a door, the doorway consists of two vertical jambs on either side, a lintel or head jamb at the top, and perhaps a threshold at the bottom. When a door has more than one movable panel, one of the panels may be called a leaf.

Excavating Machines

Excavating Machine, any machine, usually self powered, that is used in digging or earthmoving operations of some kind; the power shovel, bulldozer and grader are examples.

Power shovel, digging and loading machine consisting of a revolving deck with a power plant, driving and controlling mechanisms, sometimes a counterweight, and a front attachment, such as a boom or crane, supporting a handle with a digger at the end. The whole mechanism is mounted on a base platform with tracks or wheels. Power shovels are used principally for excavation and removal of debris. Mechanical cable-operated shovels apply engine power to the base and to the attachment by means of clutches, gears, shafts, winch drums, and cable. Electric cable-operated shovels have several electric motors supplied with current by a power line, or more rarely, by a deck-mounted generator, replacing the engine and most of the clutches, gears, and shafts of the mechanical shovel. Hydraulic shovels have engine-driven pumps to provide pressure for rams and motors. Mechanical shovels may include some electrical or hydraulic functions.

Bulldozer, also called dozer, powerful machine for pushing earth or rocks, used in road building, farming, construction, and wrecking; it consists of a heavy, broad steel blade or plate mounted on the front of a tractor. Sometimes it uses a four-wheel-drive tractor, but usually a track or crawler type, mounted on continuous metal treads, is employed. The blade may be lifted and forced down by hydraulic rams. For digging, the blade is held below surface level; for transporting, it is held at the surface level; and for spreading, it is held above the surface level, as the tractor moves forward.

Bulldozers are used for shallow digging and ditching; short-range transportation of material; spreading soil dumped from trucks; rough grading; removing trees, stumps, and boulders; and cleaning and leveling around loading equipment. A bulldozer alone can do many types of excavation, and it is useful in combination with other machinery in most excavation work.

Grader, in excavation, precision finishing vehicle for final shaping of surfaces on which pavement will be placed. Between its front and rear wheels a grader carries a broad mechanically or hydraulically controlled blade that can be extended from either side. Either end of the blade can be raised or lowered. Graders may be used for shallow ditching, but most models are used to assist other earth-moving equipment and to smooth roads, fills, and cuts.

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