Cut the 8-foot-long board into four 24-inch-long pieces, using a circular saw. These boards are the four shelves for the space saver unit.
Cut a 10-foot long, 1-by-12-inch piece of lumber in half so you have two 5-foot lengths. These are the legs of the unit.
Paint the boards with latex paint or varnish in the desired color, applying two coats of paint. Allow the paint to dry completely after each coat.
Measure the height of your toilet. Add 6 inches to this measurement. Transfer this measurement onto the two leg pieces to determine the height of the first shelf.
Determine the desired shelf height for the remaining shelves, as these depend on your storage needs. Mark the location on the legs for these shelves, placing the fourth shelf at the top of the legs.
Place a countersink bit on your drill. Adjust the bit so it is slightly longer than the length of the threaded portion of the screw. Follow manufacturer's instructions for adjusting the bit length.
Drill two holes through the legs and into the shelf edge for each shelf attachment, using the countersink bit. This bit makes a depression at the start of the drill hole that allows you to sink the screw into the wood so it doesn't protrude.
Attach the shelves to the legs by screwing the wood screws into the drilled holes. Tighten the screws completely.
Fill in the depression created by each screw with wood putty. Use a putty knife to smooth the putty so it's flush against the surface of the wood. Allow the putty to dry, then paint over the putty marks to completely camouflage the screws.
Slide the space saver in place over the toilet. Anchor the shelf to the wall with a wall anchor kit, available from hardware stores. Follow the installation instructions with the kit, as these differ among the different wall anchor designs.