Put on a pair of work gloves and safety glasses to protect your skin and eyes.
Fit two 1-by-4-by-72-inch wood rails and two 1-by-4-by-36-inch wood rails together into a 44-by-72-inch rectangle.
Place a 1/4-by-3-inch plywood triangle atop the top-right connection point of the rectangle. Drill three evenly spaced 1 1/4-inch screws into the triangle, to secure the top right connection point. Continue this step three additional times to connect all four corners of the flat frame.
Place a 1/4-by-44-by-72-inch plywood flat atop the frame. Drill a 1 1/4-inch screw into place every 6 inches around the perimeter of the frame. Repeat Steps 2 through 4 two times, to create a total of three identical flats.
Secure three 2-inch metal wheels to the bottom of a 1-by-44-inch plywood triangle platform with 1 1/4-inch screws.
Stand one flat onto the triangular platform. Secure the flat to the platform with 2-inch screws. Continue this process until all three flats stand upright and are secure upon the platform. Drill one 2-inch screw every 6 inches through the vertical rail on one flat, into adjacent rail on the flat to its right, to ensure a stable hold.
Coat each flat in Latex interior paint. Allow two hours for the flats to dry before handling.