I had originally rigged up a way to attach a curtain to the edge of the driver compartment headliner. It was okay, but it didn't slide. I had to roll or twist it up and stuff it into the gap between the crossbeam and the roof. Now I've improved it.
The first thing was to make a piece that filled the gap between the headliner and the crossbeam. The only tricky part was matching the curve of the roof. Then I attached a roller rod to it.
The tedious part was sewing the rollers to the curtain. Mama had taught me how to use a needle and thread when I was little, but my stitching isn't anything to brag about.
A curtain—particularly one in a moving vehicle—needs something to hold it back. The metal and wood hold-backs they sell for home use are too bulky. And not very manly (because that's the most important thing). So I used a cabinet handle.
That should hold everything in place, even while driving with the windows open
I rarely stealth camp, so my curtain doesn't need to be light tight. It's just for privacy. No one wants to see me naked. Unfortunately.