Question: I have found what looks like a foam sheet in the shape of a wing rib in my kit. My friend has another VMAR ARF and it has a black plactic component that also looks like a wing rib. What are these for?
Answer: These parts help seal and fit the wing root to the side of the fuselage.
Better Answer: The pre-cut foam is a gasket that can be attached to the wing root of your wing and serves as a sealing and protective gasket between the wing root and the side of the fuselage. Use silicone or latex contact cement to attach the gasket to the wing root.
The pre-molded plastic piece is a fairing that can be cut and attached to the wing root to serve as a finishing piece to enhance the appearance of the wing root to fuselage fit. This is used on fuselages that have a considerable taper or curve to them. | 
