"crush nuts" ....do they have another name?

I call them crush nuts, but can't find any reference to them on Google etc.

The things I'm referring to are small threaded "things" that are used as a captive nut in panel work. I had them on my last GU...they were provided as part of a kit for a fold-down table that was bolted on the inside of the large barn door. They were used as a method of being able to screw a retaining lug onto the top of the panel which was needed to be able to retain the table in the upright position.

What happens with these "crush nuts" (or whatever their real name is), is that you insert them into the hole of the panel and then proceed to do-up the bolt that fits it. As you do it up tight, it causes the "nut" for pull in and hold it in tight position on the panel; never to be released again.

If anybody knows the correct name and/or where I can get a few of these, it would be appreciated.

Cheers

Roachie