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after removing the vent to replace the paper filter, the machine screws do not have a nut to secure with inside the hull. How is this done ?

Others who know for sure will chime in, but there's often a small metal plate fiberglassed into the back of areas where they know things will be externally attached. If it's something that shouldn't ever see a load, like a vent cover, speakers, etc., they are sometimes also just screwed in to the hull material.

A picture would help. Are you referring to the horn grille? If so the horns are attached to a bracket that has threads for those screws. You will most likely need someone on the inside to hold the horns in place to line up the screws.

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So glad you found us Rushman.

Yes a pic may help.

And welcome aboard mate.

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