The rougher side of the file is for eventual preliminary filing of men's nails (generally thicker and harder) and toenails. The finer side allows for more precise filing. How to use: Use the lighter side with long, agile movements, from the edges towards the center to give the nails the desired shape. To keep your nails strong, avoid deeply filing the sides of the nail tip (the most fragile part). To finish, file and eliminate any roughness that may have remained by making small vertical passes, from top to bottom and vice versa (bevelling), with the tip of the file. This will also allow the 3 layers of the nail to be sealed again. If prior filing is necessary (if there is a lot to file or if the nails are hard), you can start with the rough yellow side and finish with the lighter side. assorted color