Utility Workers Union of America
AFL - CIO Local 127

Union stewards can't be everywhere at once, and they can't see or hear personally everything that goes on around the workplace.  So part of your job as an individual union member is to be on the lookout for things that the union needs to know about, and to pass along the necessary information.  If, for example, a change is made in working conditions but too long a period of time passes before a grievance is filed, it may be too late to challenge the employer's unilateral action.  So it's part of your responsibility as an individual union member to be the union's "eyes and ears" in your workplace.
-- Adapted from The Union Members Complete Guide, by Michael Mauer