An apparatus includes first and second side portions, and a horizontal portion disposed between the first and second side portions. Each side portion includes an inner wall joined to the horizontal surface, an exterior wall, and a top portion connected that define a volume within the side portion. Each side portion also includes first and second wheels within the volume, the first and second wheels having a raised wheel position and a lowered wheel position. Each side portion also has an arm coupled to the outer wall of the side portion, the arm having a first arm position and a second arm position. Movement of the arm from the first arm position to the second arm position causes the wheels to move from the raised wheel position to the lowered wheel position.