No. 71-1245. Argued September 13, 1971. Decided March 21, 1972. Leonard L. Scheinholtz, Reed, Smith, Shaw McClay, Pittsburgh, Pa. (S. G. Clark, Jr., V. L. Matera, Pittsburgh, Pa., on the brief) for American Bridge Div., U.S. Steel Corp., petitioner. Warren M. Davison, N.L.R.B., Washington, D.C. (Eugene G. Goslee, Acting Gen. Counsel, Dominick L. Manoli, Associate Gen. Counsel, Marcel Mallet-Prevost, Asst. Gen. Counsel, Madge F. Jefferson, Atty., N.L.R.B., on the brief) for respondent. James D. English