A modular running board adaptable for use with various types of vehicles having different wheel bases. In a first embodiment, the running board includes a first long board and a second long board connectable to a pick-up truck having crew cab or quad cab with four full doors. In another embodiment, the first long board is connected to a short board, and both the long board and short board are connected to a pick-up truck having an extended cab, with two full doors and two half-doors. In either of the first two embodiments, a coupling piece is used for connecting the first long board to the second long board, or the first long board to the short board. In yet another embodiment, only the first long board is connected to a vehicle, such as a pickup truck having a regular cab with two full doors only.