The Frouge Corporation (Frouge) was the general contractor on a housing project in Philadelphia. The carpenter employees of Frouge were represented by the Carpenters’ International Union (Union). Traditional jobs of carpenters included taking blank wooden doors and mortising them for doorknobs, routing them for hinges, and beveling them to fit between the doorjambs. Union had entered into a collective bargaining agreement with Frouge that provided that no member of Union would handle any doors that had been fitted prior to being furnished to the job site. The housing project called for 3,600 doors. Frouge contracted for the purchase of premachined doors that were already mortised, routed, and beveled. When Union ordered its members not to hang the prefabricated doors, the National Woodwork Manufacturers Association filed an unfair labor practice charge against Union with the NLRB. Is Union’s refusal to hang prefabricated doors lawful? National Woodwork Manufacturers Association v. N. L. R. B., 386 U. S. 612, 87 S. Ct. 1250, 1967 U. S. Lexis 2858 (Supreme Court of the United States)