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This is the retainer nut for a center high brake lamp on the roof of a ford van (2008 e350)

Here is a link showing this nut and the assembly in which it goes. In the assembly diagram its labeled "HN1"

https://parts.ford.com/shop/en/us/nut-special-7842539-1#sectionId:4188484

image from link

This retainer nut is in the roof body and accepts the screw for the center high brake lamp assembly (which you remove to change the lamp inside)

In fact, seeing it you might think it's a permanent part of the roof body, but apparently it's a part that can be replaced.

I'd like to replace one because it's come loose so trying to turn the screw, the nut rotates instead

I can reach a finger into the opening behind the brake light assembly, which I did manage to remove, and feel the tube beneath but I can't budge it, it won't come up

Are they crimped on ?

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  • When I click on that link, there is no diagram.
    – HandyHowie
    May 3 at 7:12
  • HandyHowie at the link at the left top there is an image box, and beneath the image box a row of thumbnails. Clicking the thumbnail for the diagram puts the diagram in the image box
    – k0nichiwa
    May 4 at 3:30
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Based on the shape of the "special nut" which is certainly an unusual part name, I would expect that the nut is really a rivnut. When installed, the tool pulls the portion inside the sheet metal, compressing the back side against the metal, preventing the spinning you're experiencing.

There's no documentation to support this, but it seems unlikely that the serrations on the special nut are the only thing preventing the spinning.

If the nut is not compressed in the expected manner, it may pull straight out. If it is only slightly compressed, the bulge will prevent pull-out, but not prevent the spinning when attempting to remove it.

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