There are hundreds of special purpose inserts like this... which looks very familiar.
This particular one, full threaded ID appears to be for honeycomb... large hole insert into honeycomb cavity, resting on the interior of the opposite skin.
The [2] large slots on each side of the round-flange hear are for injecting potting compound into the hole [one side]... then filling the cavity up with potting compound until the excess vents out the other slot under pressure. The compound can be a light foam foam mixture or an expanding-foam mixture.
A sample variety of these inserts can be seen as follows.
Regards, Wil Taylor
o Trust - But Verify!
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