Simply the Southern version of the touch hole pick that you see under the cheek piece on a of of Pennsylvania rifles. The feather hole is a small hole between the toe plate, and the trigger guard. The feather is used to block or clean the touch hole. If you look at the post Ken, "Packdog" had on "Another Upper East Tennessee rifle 8 pages back on this thread, you will see a Magpie feather in the feather hole. By the way that's my new baby, but Ken forgot to give me the feather, and I had to put in a turkey feather in it's place.
Bill