I was removing the bolts that attach the transmission skid plate to my Jeep Wrangler and one of the bolts would merely spin and not come out. I realized that the nutsert(rivet nut, rivnut) it was attached to was also spinning. There was no way to get this bolt and nutsert out by normal means at this point.
The way a nutsert stays in place is by expanding when the bolt in it is tightened. This one was damaged and was not going to tighten or loosen. There was some play in the area that is normally wedged in the frame rail hole. The only way to get it out was to cut it out.
Once I finished cleaning it up I replaced the nutsert and bolted it right back up.