This has been covered on the board before. To keep you hedgehogs nails a safe and healthy length the only thing you can do is trim them. Hedgies walk on the soles of their feet and if the nails are long enough to be worn down by something then they are WAY too long. Also, anything rough enough to wear down hedgies nails would be painful for the bottoms of their feet, one of our little girls ran her feet raw on her comfort wheel this weekend causing them to bleed profusely. Imagine how bad it would be on sandpaper or anything else that would be used to file down the nails..