Rule 5. In addition to the use of blue flag by day and blue light by night, as provided in Rule 26 of the Operating Rules, for the protection of persons working under or around cars, switches leading to assigned repair tracks will be kept locked with a private lock while workmen are at work on such tracks, the key to be retained and used by the person in charge of the men working on such tracks.
The Baltimore & Ohio Railroad Company, Safety Rules, Effective May 1, 1920