When jointing the blade, how important is it to keep the mill file exactly perpendicular to the blade? I've seen in virtually every treatise on the subject how to make a saw jointer out of scrap if you don't have a manufactured one, but I thought I saw in Bob Smalser's "how to" that his son was free-handing it.
Given that by the time you're done you're going to have all the resultant flats filed off anyway, it doesn't seem to me that a perfectly square jointing method is necessary.
Is the jointer then more for ease of use; to be able to hold the file more easily?