 When an employer gave work to one union, a rival union would strike to force the employer to give the work to its members.These jurisdictional strikes often led to the shut-down of entire construction sites, throwing all employees out of work.The winner of a jurisdictional strike more often than not was also the union which had more power—either more members, or members whose work was critical to construction work (such as "operating engineers")—rather than the union whose workers were best suited for the job.