The Mystery of the Sealed Box The box is sealed because we don't care what's in it. And in a sense it's not mysterious because all we're doing is looking at paths on the surface of the box. When a path meets an edge, it just keeps going. If we unfold the side of the box, the path is really "straight", i.e., it's a geodesic. And to keep things simple, our paths will always meet edges at an angle of {$45^\circ$}.