A cover assembly includes a support bracket from which a cover board is selectively suspended. The support bracket is itself mounted to a third rail or contact rail by a clip which cooperates with the bracket. The cover board is held in place on the bracket by an upper flange which has a tapered or V-shaped front wall, as well as a tapered bottom wall. A flag holder, which can be selectively attached to the bracket, includes a first section with an engaging member that cooperates with an engaging member located on the support bracket, a center section including a through bore for holding a flagstaff of a safety flag and a second end section. The second end section is adapted to attach the flag holder to a different type of cover board support bracket.