Clecos are those shiny cylindrical things you see in the photo. They are best known in aviation, where they are used in the construction of aluminum airplanes. They have expanding tips, sort of fingers that spread apart and pull sheet metal assemblies together. When you compress them (with Cleco pliers) they retract and you can pull them out of a hole. Imagine an airplane skin, with all the holes match-drilled to the structure underneath. Fill all (or most) of the holes with Clecos to hold everything in alignment. Then remove them as you rivet it together. I've used them for holding fender flares in place while I drive rivets or install screws. And for holding the skins of my RV7 together as I build it. But's that's a different money pit story...