Did you know chestnuts, which is the horny growths on the insides of your horse's legs, are as unique as fingerprints for your horse? And, it can be used for identification. Chestnuts are like your thumb or big toe that no longer functionable through evolution.
While "smoothing" the chestnuts is not a health necessity as long as it does not get caught on something and ripping. If you prefer the smooth it down, you need to soften the chestnut to allow them to crumble. You can apply the Sore No More Spots Salve on it to soften it for a few days. Once soften, you can try to peel it off or run a rubber curry over them but don't try to remove more than ONE layer at a time. Then repeat the process until the chestnuts are flat. To maintain it, rub a bit of Sore No More sports Salve once or twice a week.