When the bottom edge of a model rocket part conforms to the shape of the curved body tube, we call this a conformal part. This includes wide parts, like thick fins, surface details like electrical tunnel covers, or simulated cockpits. The reason to make conformal parts is that they are much stronger, lighter, and they look better because there are not unsightly gaps under the edges. This video shows you how simple it is to make conformal parts. Basically, all you need is some sandpaper, and a body tube.