Not all the period stools we studied had this chamfer on the interior corner of the stiles, but many did (some tables, too). Never did we find one in which some stiles had chamfers and others did not. It was either all or nothing. This led us to think it was intentional. Then we began to wonder what its use might be. We might be wrong, but it works for orientating your parts during construction – even if that was not its original purpose.
— Jennie Alexander and Peter Follansbee from their forthcoming book on joint stools