There originally was a fiber gasket between the extension and door and it was not really visible. I owned a '46 Fleetmaster for 45 years that I sold in 2018 and when I originally rebuilt it in 1975 I never replaced the gasket and never had a problem of rattling, vibration or damage to the paint. I put almost 90,000 miles on the car, drove it through numerous rain storms and never had an issue. It was my opinion, all this gasket did was retain moisture and promote rust and is not really necessary. Over the years I had occasion to remove the extensions for two repaints, and never found a scratch or rust.
