Dashboard trim insert fasteners that hold it?

[Mechanized]

My 81 C10 has the long dashboard trim insert piece on the passenger side, the trim itself holds the two air vents; there are a handful of plastic prongs sticking out of the trim that go into the holes in the dash and then through the air vent tubes behind the dash to hold the vent tubes in place; my trim had zero hardwear on it; however, on ebay I saw a trim piece that had these washer things on each prong, they looked like a washer but then with five or so teeth on the inside so they will bite into the plastic prong and hold it in place. Hard to describe, but I dont know the name of these washer things, does anyone know what these are formally called or where to find them?

Second does anyone make a good interior fastener assortment kit for the 81 roughly C10's - especially focusing on the dash/instrument area?

Thanks for any help!

[VileZambonie]

Google: thread cutting nuts

[VileZambonie]

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[Mechanized]

Google: thread cutting nuts

Thanks Vile, I just found a new picture of the dash insert and this one has the cutting nuts as your saying - so thinking the last picture I saw of one with more of a washer type must be wrong; the issue now is which size cutting nuts - looks like there is three different sizes 1/4 3/16 etc.

[ehjorten]

My square-bodies all have the thread-cutting nuts (AKA sheetmetal nuts).

[Mechanized]

My square-bodies all have the thread-cutting nuts (AKA sheetmetal nuts).

Thanks Ehjorten, just found a trim piece on ebay that had the air vents actually attached still and it is using nuts - not washer type, so this is starting to make more sense, guess if you actually attach the vent ducts first then put in dash attached it would work - was thinking there would be no room to screw the nut type on behind the dash if that makes sense.

[VileZambonie]

These are the ones I have in stock

[Mechanized]

These are the ones I have in stock

Thanks, yeah I think 3/16 like your showing are the ones - I believe I can grab some of these locally, gonna check tomorrow; took my dash and instrument area apart further more earlier and found a few of these nuts lying behind there with the plastic prongs broken off in them, so thats gotta be the ones used.