A grease gun is a common workshop

Workshop

A workshop is a room or building which provides both the area and tools that may be required for the manufacture or repair of manufactured goods...

 and garage

Automobile repair shop

An automobile repair shop is a place where automobiles are repaired by auto mechanics and electricians.- Types :The automotive garage can be divided in so many category....

 tool

Tool

A tool is a device that can be used to produce an item or achieve a task, but that is not consumed in the process. Informally the word is also used to describe a procedure or process with a specific purpose. Tools that are used in particular fields or activities may have different designations such...

 used for lubrication

Lubrication

Lubrication is the process, or technique employed to reduce wear of one or both surfaces in close proximity, and moving relative to each another, by interposing a substance called lubricant between the surfaces to carry or to help carry the load between the opposing surfaces. The interposed...

. The purpose of the grease gun is to apply lubricant through an aperture to a specific point, usually on a grease fitting

Grease fitting

thumb|right|Grease nipple on a [[bearing |bearing]]A grease fitting, grease nipple, Zerk fitting, or Alemite fitting is a metal fitting used in mechanical systems to feed lubricants, usually lubricating grease, under moderate to high pressure, into a bearing using a grease gun...

. The channels behind the grease nipple lead to where the lubrication is needed. The aperture may be of a type that fits closely with a receiving aperture on any number of mechanical devices. The close fitting of the apertures ensures that lubricant is applied only where needed. There are three types of grease gun:

1. Hand-powered, where the grease is forced from the aperture by back-pressure built up by hand cranking the trigger mechanism of the gun, which applies pressure to a spring mechanism behind the lubricant, thus forcing grease through the aperture.
2. Hand-powered, where there is no trigger mechanism, and the grease is forced through the aperture by the back-pressure built up by pushing on the butt of the grease gun, which slides a piston through the body of the tool, pumping grease out of the aperture.
3. Air-powered (pneumatic), where compressed air is directed to the gun by hoses, the air pressure serving to force the grease through the aperture. Russell Gray, inventor of the air-powered grease gun, founded Graco
   Graco (fluid handling)
   Graco is a manufacturer of fluid-handling systems and products based in Minneapolis, Minnesota.-History:Russell Gray, a Minneapolis parking lot attendant, founded Gray Company, Inc. in 1926 with his brother Leil Gray to produce and sell Russell's air-powered grease gun, invented in response to cold...
   
    based on this invention.

The grease gun is charged or loaded with any of the various types of lubricants, but usually a thicker heavier type of grease

Grease (lubricant)

The term grease is used to describe semisolid lubricants. Although the word grease is also used to describe rendered fat of animals, in the context of lubrication, grease typically applies to a material consisting of a soap emulsified with mineral or vegetable oil...

 is used.

It was a close resemblance to contemporary hand-powered grease guns that gave the nickname to the World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

-era M3 submachine gun

M3 submachine gun

The M3 was an American .45-caliber submachine gun adopted for U.S. Army service on 12 December 1942, as the United States Submachine Gun, Cal. .45, M3. The M3 was designed as a more cost-effective alternative to the Thompson, optimized for mass production...

.