 Theoretically, hide glue is weaker than the body's wood, so as the top or back shrinks side-to-side, the glue holding it lets go, so the plate does not crack.Cellists repairing cracks in their cello do not use regular wood glue, because it cannot be steamed open when a repair has to be made by a luthier.Traditionally, bows are made from pernambuco or brazilwood.