Provisions in collective agreements designed to protect the institutional authority of the union,

Examples of union security clauses are: closed shop, an agreement between union and employer that the employer may hire only union members and retain only union members in the shop; preferential hiring, an agreement that an employer, in hiring new workers, will give preference to union members: union shop, an agreement that the employer may hire anyone he wants, but all workers must join the union within a specified time after being hired and retain membership as a condition of continuing employment; maintenance of membership, a provision that no worker must join as a condition of employment, but all workers who voluntarily join must maintain their membership for the duration of the contract in order to keep their jobs. (See also Checkoff, Closed Shop, Maintenance of Membership, Rand Formula, Union Shop, Modified Union Shop.)