What is Hiring Hall?

Legal Definition
In organized labor, a hiring hall is an organization, usually under the auspices of a labor union, which has the responsibility of furnishing new recruits for employers who have a collective bargaining agreement with the union.

The employer's use of the hiring hall may be voluntary, or it may be compulsory by the terms of the employer's contract with the union (or, in a few cases, the labor laws of the jurisdiction in question). Compulsory use of a hiring hall effectively turns employers into a closed shop because employees must join the union before they can be hired. In the United States, this occurs mainly in the trade unions. This actually benefits contractors who hire employees for the duration of a specific job. The reason for this is because the union makes sure the individuals sent to the job site are properly trained and qualified to do the work. Additionally, the union will also maintain employment records on the individual. If someone has a history of unreliability or disciplinary problems, for example, individual contractors may not know about it. However, the union will maintain a disciplinary file on the individual and (if the situation calls for it) will revoke the individual's union card in essence, firing them. The benefit to the workers is that they maintain health insurance and a retirement through the union. Those benefits are paid for by the contractor as they would be by any other employer, but the money is paid to the union so health insurance does not lapse while the worker is between jobs. By contrast, the prevalence of compulsory hiring hall arrangements in Canada varies from trade to trade and from province to province, since labor law there is under provincial jurisdiction. The situation in Europe also varies from country to country.

The presence of a hiring hall places the responsibility on the union to ensure that its members are suitably qualified and responsible individuals before assigning them to an employer. The union will often enforce a basic code of conduct amongst its members to ensure smooth operation of the hiring hall (to prevent members from double-booking, for example). If a hiring hall is reputable, the relationship between the union and the employer can be relatively harmonious. Many employers, particularly those who require skilled tradespeople, prefer to use the services of a reputable hiring hall rather than attempt to find qualified, responsible recruits by themselves.

Hiring halls are generally most prevalent in skilled trades and where employers need to find qualified recruits on short notice.
-- Wikipedia
Legal Definition
A system whereby a union refers potential employees to an employer. Also may refer to a system of union work permits. Such referals and work permits may not discriminate based on membership in the union.