Of course, the modern instrumental bow isn't flat, but inverted, with the bend *facing* the hair. (That, in itself, must have been a huge breakthrough). This makes sense from a mechanical standpoint, because the hair flexes toward the bow, as opposed to away from it, as in an archer's bow. It seems to me, though, that I have seen primitive stringed instruments with concave bows where the 'hair' contacts the string from below, but it also seems to me I could be wrong.