Foot stools have many uses. Children use them when they sit in a normal chair and their feet don't reach the floor. Classical guitarists use them to elevate one leg, to position the instrument properly. And homeowners use them to get to that shelf that is just out of reach or as a place to rest their feet. A simple wooden foot stool is easy to build.
Put a layer of glue on one end (the endgrain) of one of the 12-inch boards. Place it against one end of the 18-inch board, forming an L shape, and nail the long board to the short board using three or four finishing nails. Use the damp cloth to wipe off any excess glue that squeezes out of the joint.
Repeat with the other 12-inch board on the other end of the long board. The three boards should now form a U shape -- a long top with two legs attached.
Lay the U on its side and put a layer of glue along the edge of the top and about 2 inches down the edge of each of the legs. Place one of the 1-by-4 boards on this glued area, setting the long edge flush with the top of the long board. Nail this narrow piece to the top and legs, and then wipe off any excess glue.
Repeat with the remaining 1-by-4 on the other side of the stool. Let the glue dry.
Drive the heads of all the finishing nails 1/8 inch below the surface of the wood, using a hammer and nailset. Fill the holes with the wood putty, following the manufacturer's instructions. Let the putty dry.
Sand the entire stool lightly to smooth the putty even with the wood surface. Wipe off any sawdust, and apply the finish to the stool. Let it dry.
Drill two holes on the bottom edge of each leg -- one on each side, as close to the outside edges as possible -- for a total of four holes. These are for the furniture glides. Screw them in, and your foot stool is done.
Use any finish you like. Paint and stain both work well. The combination of nails and glue makes the stool much stronger than it would be with just nails. The legs do not have to be placed right at the end of the top; they can be placed about 1 inch from each end. It is a matter of preference.
You do not need to use furniture glides, but they will keep the stool from sliding on smooth surfaces. Place them as close as possible to the outside edges, to make the stool as stable as possible.