On the basis of observation, Wilbur concluded that birds changed the angle of the ends of their wings to make their bodies roll right or left. The brothers decided this would also be a good way for a flying machine to turn—to "bank" or "lean" into the turn just like a bird—and just like a person riding a bicycle, an experience with which they were thoroughly familiar. Equally important, they hoped this method would enable recovery when the wind tilted the machine to one side (lateral balance). They puzzled over how to achieve the same effect with man-made wings and eventually discovered wing-warping when Wilbur idly twisted a long inner-tube box at the bicycle shop.