Here I have placed a clamp in the center of the header rail to hold the header rail securely to the top of the windscreen frame. The clamp is optional, but it does help to firm things up a bit while work is in progress. The black marks on the front of the header rail are just stains from a little rusting of the staples used in the prior fabric installation, not a big deal as the wood is still in excellent condition.

The fabric wrap piece is placed here under the header rail. It is positioned with the drop flap on the bottom and to the front of the windscreen frame. I have measured and placed a mark at the center of the header rail and at the center of the wrap strip. This is to get the wrap strip centered on the top of the windscreen. It's still a good idea to check underneath before starting the stapling, just to be sure the ends of the drop flap are positioned symmetrically with the ends of the windscreen frame.