Determine the two most played sports in your gymnasium. Find the measurements online for the boundary lines for each of these two sports.
Measure across your gymnasium floor to find the corner points for each line for the most prevalent sport to be played. Use your chalk box to extend the lines to their full length. Place 3 inch tape on each side of every line to form your outlines. Paint the lines with the darker of your two colors using your 3 inch roller. Apply three coats of paint to each line after allowing each coat to dry completely before application of the next. Remove the tape from the floor gently after the final coat is completely dry.
Measure the lines for your second sport. Extend the lines with your chalk box and place your tape outline to the floor. Paint these lines with the lighter of your two colors. Apply three coats of paint to every line. Allow each coat to dry completely before applying the next. Remove the tape gently after the final coat is dry.
Wrap a rag around your index finger and dip it into paint thinner. Wipe away imperfections in your lines with the thinner soaked rag. Place your roller pan into the empty 5 gallon bucket, add 1/2 gallon of thinner to the bucket and clean your roller pan thoroughly with thinner.
Apply threecoats of polyurethane to the entire floor to seal the wood and preserve your lines. Wait for each coat to dry before application of the next. Apply polyurethane to the outer edge of the floor and around obstacles in the floor with your paint brush. Clean your brush, pan and roller with thinner in your cleaning bucket between each coat to get a smooth finish.