Well here you go, the secret project will be revealed. I have side trim but no fasteners.....well one. But it was rusted beyond belief. So check this out. I had seen a thread where an enterprising young man had made his own. I chose a different route. Adapt an existing common part to a different purpose!
You take your nasty twisty, secure it in a small vice, and with a crap chisel, open that bad boy up.
Here is what you end up with. You starting to get the idea?

Look at that fit!!

Side trim fasteners recycled from junk parts!!! The fit is slightly looser than the stock fastener, but a hell of a lot less work than making them from scratch.
Cheers,
Roman
