What's the name of this bolt/nut combination? It accepts a 3/16 hex on both ends and is used frequently in assembling this play set. The thread pitch is 1/4-20. The nut is hollow, allowing you to put an hex key all the way through it.

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  • Might be a specially made non cloth/skin catching safety bolt/nut. Closest to a round head bolt.
    – crip659
    May 1, 2022 at 16:28
  • Also, the design seems intended to prevent over-tightening, because attempting that would force the Allen key out. May 1, 2022 at 16:43
  • this may help ... duckduckgo.com/…
    – jsotola
    May 1, 2022 at 17:38
  • @jsotola including the search terms themselves in your comment text would be a courtesy. I can hover over the link to see them on my desktop machine, but that's hard to do on a touch-screen-only device and not everyone is willing to click a search link where they can't see the search terms.
    – FreeMan
    May 2, 2022 at 13:23

1 Answer 1


I was able to find something close enough to the bolt in question, thanks to the comment from @jsotola. They have many names, but this is what was most common.

Socket Button Barrel Nuts:

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