Prefabrication is the practice of assembling components of a structure in a factory or other manufacturing site, transporting complete assemblies or sub-assemblies to the construction site where the structure is to be located. The term is used to distinguish this process from the more conventional construction practice of transporting the basic materials to the construction site where all assembly is carried out; the term prefabrication applies to the manufacturing of things other than structures at a fixed site. It is used when fabrication of a section of a machine or any movable structure is shifted from the main manufacturing site to another location, the section is supplied assembled and ready to fit, it is not used to refer to electrical or electronic components of a machine, or mechanical parts such as pumps and compressors which are supplied as separate items, but to sections of the body of the machine which in the past were fabricated with the whole machine. Prefabricated parts of the body of the machine may be called'sub-assemblies' to distinguish them from the other components.

An example from house-building illustrates the process of prefabrication. The conventional method of building a house is to transport bricks, cement, sand and construction aggregate, etc. to the site, to construct the house on site from these materials. In prefabricated construction, only the foundations are constructed in this way, while sections of walls and roof are prefabricated in a factory, transported to the site, lifted into place by a crane and bolted together. Prefabrication is used in the manufacture of ships and all kinds of vehicles and machines where sections assembled at the final point of manufacture are assembled elsewhere instead, before being delivered for final assembly; the theory behind the method is that time and cost is saved if similar construction tasks can be grouped, assembly line techniques can be employed in prefabrication at a location where skilled labour is available, while congestion at the assembly site, which wastes time, can be reduced. The method finds application where the structure is composed of repeating units or forms, or where multiple copies of the same basic structure are being constructed.

Prefabrication avoids the need to transport so many skilled workers to the construction site, other restricting conditions such as a lack of power, lack of water, exposure to harsh weather or a hazardous environment are avoided. Against these advantages must be weighed the cost of transporting prefabricated sections and lifting them into position as they will be larger, more fragile and more difficult to handle than the materials and components of which they are made. Prefabrication has been used since ancient times. For example, it is claimed that the world's oldest known engineered roadway, the Sweet Track constructed in England around 3800 BC, employed prefabricated timber sections brought to the site rather than assembled on-site. Sinhalese kings of ancient Sri Lanka have used prefabricated buildings technology to erect giant structures, which dates back as far as 2000 years, where some sections were prepared separately and fitted together, specially in the Kingdom of Anuradhapura and Kingdom of Polonnaruwa.

After the great Lisbon earthquake of 1755, the Portuguese capital the Baixa district, was rebuilt by using prefabrication on an unprecedented scale. Under the guidance of Sebastião José de Carvalho e Melo, popularly known as the Marquis de Pombal, the most powerful royal minister of D. Jose I, a new Pombaline style of architecture and urban planning arose, which introduced early anti-seismic design features and innovative prefabricated construction methods, according to which large multistory buildings were manufactured outside the city, transported in pieces and assembled on site; the process, which lasted into the nineteenth century, lodged the city's residents in safe new structures unheard-of before the quake. In Portugal, the town of Vila Real de Santo António in the Algarve, founded on 30 December 1773, was erected through the use of prefabricated materials en masse; the first of the prefabricated stones was laid in March 1774. By 13 May 1776, the centre of the town had been finished and was opened.

In 19th century Australia a large number of prefabricated houses were imported from the United Kingdom. The method was used in the construction of prefabricated housing in the 20th century, such as in the United Kingdom as temporary housing for thousands of urban families "bombed out" during World War II. Assembling sections in factories saved time on-site and the lightness of the panels reduced the cost of foundations and assembly on site. Coloured concrete grey and with flat roofs, prefab houses were uninsulated and cold and life in a prefab acquired a certain stigma, but some London prefabs were occupied for much longer than the projected 10 years; the Crystal Palace, erected in London in 1851, was a visible example of iron and glass prefabricated construction. The most used form of prefabrication in building and civil engineering is the use of prefabricated concrete and prefabricated steel sections in structures where a particular part or form is repeated many times, it can be difficult to construct the formwork required to mould concrete components on site, delivering wet concrete to the site before it starts to set requires precise time management.

Pouring concrete sections in a factory brings the advantages of being able to re-use moulds and the concrete can be mixed on the spot without having to be transported to a

Meisterstiche (Dürer)

The Meisterstiche by Dürer are three of his most famous engravings. They are Knight and the Devil, Melencolia I and St. Jerome in His Study; these three large prints are grouped together because of their perceived quality and unity of meaning, although this latter is a matter of scholarly dispute. Panofsky has described them as showing meticulous care in execution and have complexity and significance in terms of iconography. Panofsky while recognising that these are Durer's "most famous engravings" and are "not unjustly, known as his "Meisterstiche" notes that they "have no appreciable compositional relationship with one another" and should not, in any technical sense be "considered as "companion pieces", they do, Panofsky argues form "a spiritual unity". Here Panofsky refers to Friedrich Lippmann's noticing of the scholastic classification of the virtues they represent; the Knight showing "the life of the Christian in the practical world of decision and action". Jerome showing "the life of the Saint in the spiritual world of sacred contemplation".

Grigg, Robert "Studies on Dürer's Diary of His Journey to the Netherlands: The Distribution of the" Melencolia I"." Zeitschrift fur Kunstgeschichte, 398-409. Filippi and Michael Friel. Albrecht Dürer's Meisterstiche: proposal for an historical-epochal reading. University of Chicago, Chicago Lippmann, F. Zeichnungen von Albrecht Durer in Nachbildungen, Berlin

Fort Klock

Fort Klock, a fortified stone homestead in the Mohawk River Valley of Upstate New York, was built c.1750 by Johannes Klock, is a good example of a mid-18th century fortified home and trading post, seeing use during the French and Indian War and the American Revolutionary War The fort is located at 7203 Route 5 two miles east of the Village of St. Johnsville, New York. Fort Klock is part of a 30-acre complex that includes the historic homestead, a renovated Colonial Dutch Barn, blacksmith shop, 19th-century schoolhouse; the site is open seasonally as a living museum. The fort was declared a National Historic Landmark in 1972. Fort Klock is located between New York State Route 5 and the Mohawk River, two miles east of the village of St. Johnsville; the fort is a single-story stone structure, built in an L shape and set in part on bedrock, in part on a stone foundation. The walls are quite thick, with numerous loopholes. There are two chambers on the main floor, their walls finished in plaster. Bedrooms are located in the attic spaces.

A door on the east side provides access to the basement, divided into two chambers, separated by a heavy stone wall. One of these has a small spring-fed pool; the house was built in 1750 by Johannes Klock. Klock used the building as a frontier residence and trading post for dealing with local Native Americans. In 1776, Klock further fortified the premises. Klock was an active partisan in the American Revolutionary War, serving in the local militia at the 1777 Battle of Oriskany; the surrounding area was raided by British-led Native Americans between 1778 and 1782, actions in which many houses and crops were burned. In October 1780, one of these raiding bands was confronted by state militia in a field just to the west, in what is now known as the Battle of Klock's Field; the property was occupied by Klock descendants until the 1950s, at which time it was abandoned and declined. It was restored by a local nonprofit organization, given the property by the last Klock owners in 1973. There were two distinct places referred to as Fort Klock during the Revolutionary War: Johannes' house and the home of his brother, Conradt Klock, located in Reimensnyders Bush or Glen's Purchase to the north of Little Falls, New York.

The Klock Forts were but two of the plethora of fortifications in the central and upper Mohawk Valley, built to resist raids from the British and their allies. Media related to Fort Klock at Wikimedia Commons Official website Historic American Buildings Survey No. NY-370, "Fort Klock, U. S. Route 5, Saint Johnsville, Montgomery County, NY", 18 photos, 2 data pages Fort Klock Historic Restoration Photos of the burning of the Harvest Reenactment at historic Fort Klock Fort Klock Historic Restoration I Spy in St. Johnsville Information and other Revolutionary sites on route Revolutionary War Heritage Trail