These principles have guided the Administrator in the enforcement of the Act. Two cases decided by the U.S. Supreme Court further illustrate the types of activities which are considered an integral part of the employees' jobs. In one, employees changed their clothes and took showers in a battery plant where the manufacturing process involved the extensive use of caustic and toxic materials. (Steiner v. Mitchell, 350 U.S. 247 (1956).) In another case, knifemen in a meatpacking plant sharpened their knives before and after their scheduled workday (Mitchell v. King Packing Co., 350 U.S. 260 (1956)). In both cases the Supreme Court held that these activities are an integral and indispensable part of the employees' principal activities.