Abstract: A display board assembly includes a map rail and a supplemental display board mounted thereto. The map rail includes a top track defined by a top support rail and a top guard rail, and a bottom track defined by a bottom support rail and a bottom guard rail. The supplemental display board includes a wheeled mounting assembly on a rear surface thereof, the wheeled mounting assembly including: a top wheel forced to engage the top track and confined by the top guard rail, and a bottom wheel forced to engage the bottom track and confined by the bottom guard rail, wherein the supplemental display board is slidable on the top wheel and bottom wheel to different lateral positions on the map rail.