 In Europe and North America, common woods such as maple, ash, elm, and oak make excellent flat bows, and are far easier to obtain than good-quality yew.The fibres on the back of a self bow must be, so far as possible, continuous.This may be achieved by using the outer, under-bark surface of the tree as the back of the bow (convenient with most white woods), or by the painstaking process of removing outer growth rings (often used with yew and osage orange), or by making or following a cut or split surface which happens to have continuous grain (a usual approach if starting with commercially sawn wood).