A rail system for mounting to a vehicle, comprising: a frame mountable in the cargo area of a vehicle, the frame comprising: a left rear support leg and a right rear support leg, each rear support leg having a bottom end adapted to attach to the vehicle, and a top end, a rear horizontal beam coupled to the top end of each rear support leg, a left front support leg and a right front support leg, each front support leg having a bottom end adapted to attach to the vehicle, and a top end, a front horizontal beam coupled to the top end of each front support leg, a left side horizontal beam coupled to the left rear support leg and the left front support leg, and a right side horizontal beam coupled to the right rear support leg and the right front support leg; a first fixed rail mounted to the left rear support leg and left front support leg, the first fixed rail comprising inside, top, and bottom faces with a plurality of bearings mounted to each of the inside, top, and bottom faces, and a back face with a back plate mounted to the back face; a first sliding rail slidable on the first fixed rail, the first sliding rail comprising a utility side and a groove side, the groove side comprising a plurality of grooves for receiving the plurality of bearings coupled to the first fixed rail, providing for longitudinal movement of the sliding rail in relation to the fixed rail; a second fixed rail mounted to the left rear support leg and left front support leg; a second sliding rail slidable on the second fixed rail; and a wall panel coupled to the first and second sliding rails. a frame mountable in the cargo area of a vehicle, the frame comprising: a left rear support leg and a right rear support leg, each rear support leg having a bottom end adapted to attach to the vehicle, and a top end, a rear horizontal beam coupled to the top end of each rear support leg, a left front support leg and a right front support leg, each front support leg having a bottom end adapted to attach to the vehicle, and a top end, a front horizontal beam coupled to the top end of each front support leg, a left side horizontal beam coupled to the left rear support leg and the left front support leg, and a right side horizontal beam coupled to the right rear support leg and the right front support leg; a left rear support leg and a right rear support leg, each rear support leg having a bottom end adapted to attach to the vehicle, and a top end, a rear horizontal beam coupled to the top end of each rear support leg, a left front support leg and a right front support leg, each front support leg having a bottom end adapted to attach to the vehicle, and a top end, a front horizontal beam coupled to the top end of each front support leg, a left side horizontal beam coupled to the left rear support leg and the left front support leg, and a right side horizontal beam coupled to the right rear support leg and the right front support leg; a first fixed rail mounted to the left rear support leg and left front support leg, the first fixed rail comprising inside, top, and bottom faces with a plurality of bearings mounted to each of the inside, top, and bottom faces, and a back face with a back plate mounted to the back face; a first sliding rail slidable on the first fixed rail, the first sliding rail comprising a utility side and a groove side, the groove side comprising a plurality of grooves for receiving the plurality of bearings coupled to the first fixed rail, providing for longitudinal movement of the sliding rail in relation to the fixed rail; a second fixed rail mounted to the left rear support leg and left front support leg; a second sliding rail slidable on the second fixed rail; and a wall panel coupled to the first and second sliding rails.