In the required items list on Towerhobbies, it lists 4-40 x 1-1/4" bolt and blind nut set. In the Accessories Needed list it has Great Planes Bolt Set/Blind Nuts 4-40x1-1/4" (4) and Great Planes Bolt Set/Locknuts 4-40x1" (4). So do i need both or just the 1-1/4" Blindnut set. Also, is 4 enough of each? And finally, what are these used for (both: Blindnut and locknut?)