It is important to sand the floor several times with different grades of sanding paper. The first sanding is with a rough grade of paper according to the condition of your floor. This will remove the existing finish and remove a thick layer in order to penetrate the bare wood. The next sanding stages are important in order to achieve smoothness and create a level surface for the application of the finish. The edges must be sanded with a special machine. Areas that are hard to reach will be hand scraped.