I have made gaskets by using RTV silicone. Just make sure you coat any surface you don't want it adhering to with vaseline. (Maybe another use for WD-40 also.) Wipe the vaseline off so it's only a thin coating. Make sure you have your part shimmed properly to achieve the thickness you want. Goob it up with the silicone and mount it. (You can use a finger to go around the bead and smooth it, or just wait to trim it later. I usally smooth the bead and trim the little excess that squeezes past my finger later.) Go out there the next day, disassemble it and trim the gasket as needed. An X-Acto knife works really well. For larger areas you may have to wait up to a week to allow adequate cure time. The RTV is usually available in a number of colors too.

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Burma-Shave (1947)