Soldiers are generally billeted in barracks or garrisons when not on combat duty, although in some armies soldiers with families are permitted to maintain a home off-post. Used for a building, the term is more commonly used in British English; United States standard terms are quarters, barracks, "Single (Soldier) Housing" or "Family Housing".
British history 
Originally, a "billet" (from the French) was a note, commonly used in the 18th and early 19th centuries as a "billet of invitation." A particular use of the word in this sense is to denote an order issued to a soldier entitling him to quarters with a certain person. From this meaning, the word billet came to be loosely used of the quarters thus obtained. Repeated petitions against the practice of billeting, starting in the 16th century, culminated in its outlawing in 1689 as an extension of a section of the Petition of Right 1563.
During wartime, civilians who have been evacuated from a city in danger of attack are billetted in communal shelters or in the homes of individuals. The practice of billetting evacuees was widespread in Britain during World War II, particularly during the Blitz, when children and other non-essential persons in major cities were sent to rural areas for safety.
In European countries since the formation of regular forces the Quartermaster was an occupation and a rank of the individuals responsible for provision of sleeping quarters as well as other provisions for regular time troops.
United States usage 
One of the major grievances of the American colonists against the British government which led to the American Revolutionary War was the quartering of soldiers in civilian homes. As a result, the Third Amendment to the United States Constitution provides restrictions on the manner in which the Federal government of the United States may require civilians to provide housing for American soldiers.
Billet can mean a personnel position, assignment, or duty station which may be filled by one person, commonly used by the United States Navy, the United States Marine Corps, and the United States Coast Guard. It may also refer in all the armed forces to the individual bunk or bed.
Billet can also refer to the position and weapons of the members of a unit. For example, the billets of a fireteam include a fireteam leader (M16), a rifleman (M16), an automatic rifleman (M249), and a grenadier (M16 with M203 grenade launcher).
Other usage 
In Spain the noble officers of royal tercios were billeted in the homes of the affluent and well-to-do of the cities/towns they were stationed in. This usage is employed as a plot device in the Barber of Seville.
In Canada, the term is widely used in conjunction with housing visiting performers from theatrical or musical tours, such as for a Fringe theatre festival or a choir festival. Students travelling for a band or choir tour may billet with members of the host band or choir.
In copper production, a billet is a 30' log, about 8" diameter, of pure copper.
The expression "billet" is also used for an exchange student.
Amateur sports 
In North America, billet families offer room and board to junior ice hockey players (or Under-20 athletes from other sports, such as soccer). who leave home to join elite teams in other towns. Coaches are often involved with matching a player to a billet family. The objective of a billet family is to provide a "home away from home" for young players during the season. However, exaggerated fears over child safety in amateur sports in Canada drastically curtailed billeting practice. Many places do not billet, while other clubs through their provincial sports' bodies have instituted mandatory criminal record checks for all involved in amateur sports, including coaches, volunteers and anyone over eighteen years of age from the host family.
||This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (September 2009)|
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.
- Detailed history of the practice as of the early 1900s
|Wikisource has the text of the 1911 Encyclopædia Britannica article Billet.|
|Wikisource has the text of the 1911 Encyclopædia Britannica article Billeting.|
- "Copper Production from Ore to Finished Product". Retrieved 10 November 2012.
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