attaching sail panel boards

I'm putting together a 1970 Dart 2 dr Hardtop. Time to put the sail panel boards in place. There is what appears to be a nail on each side in the metal structure of the car. I can feel behind and it is long, pointed and doesn't seem to have threads. The head doesn't have a phillips or slot, just blank like a nail head. You can spin it and move it in and out to some extent , but they don't want to come out. What are these things and what do you do to install new sail panel boards? If no one has the magic bullet I'll post photos tomorrow.