Explanation: In a collective bargaining agreement, a union shop clause requires all new employees to join the union within a defined interval. In all industries except construction, this interval must be at least thirty days. In construction, it must be at least a week. A maintenance of membership clause requires employees who choose to join the union to remain enrolled until the union contract expires. However, this clause does not force employees to join the union in the first place. A closed shop clause requires any new employees to join the union. A contract administration clause contains all the administrative details.