The petitioner, W-I Canteen Service, Inc. (Canteen), seeks review of an order of the National Labor Relations Board. The Board has cross-applied for enforcement of its order. The Board found that Canteen violated sections 8(a) (1) and (3) of the National Labor Relations Act by discharging and otherwise penalizing employees for engaging in a sympathy strike. The determinative issue is the legality of the strike under two collective bargaining agreements negotiated by the petitioner and Retail Clerks Local 1354. Canteen argues that the agreements clearly and unequivocally waived the right to engage in sympathy strikes at its premises and that the Board's interpretation of the agreements was erroneous. Also at issue is the Board's determination that Canteen violated section 8(a)(1) of the Act by coercively interrogating one of its employees about her union activities. I. Facts A. The Collective Bargaining Agreements The petitioner, Canteen, services and maintains vending machines in the Rockford, Illinois, area. At its Rockford plant, Canteen and the Retail Clerks Union Local 1354 have been parties to three separate collective bargaining agreements covering three separate bargaining units. One agreement covers the service and maintenance unit. Members of this unit report to Canteen's Rockford facility to pick up goods for delivery to the premises of customers. Three members of this unit report directly to a nearby Chrysler plant and remain there all day without reporting to the Canteen Rockford facility. Another bargaining agreement covers members of the bakery unit, which produces some of the goods sold in the vending machines. The third agreement covers clerical workers. The service and maintenance agreement (Service Agreement) was first negotiated in 1968 and was renegotiated in 1969, 1972, and 1975. The bakery unit agreement (Bakery Agreement) was first negotiated in 1968 and was renegotiated in 1971 and 1974. The clerical unit agreement was entered into for the first time in 1976.