The ergot (on a horse that has not been clipped, as in the photo to the Right) is generally hidden in the fetlock hair. But on this horse, it can be found on the back of the pastern joint, where the light/ dark hairs meet.
The ergot continually grows, and feels rough, almost like a big wart.
If the ergot does not shed regularly on it's own, you must help by pulling off the excess.
It is believed the Ergot is a vestigal "toe" leftover from the early equine, the Eohippus. This means, at one point, it was a useful part of the equine anatomy, but is no longer believed to perform any useful function.