Anyone know how the "nuts" into which the license plate screws screw are fixed in the trunk lid? MB obviously doesn't understand Galvanic action as the nuts are lead or some soft metal while the screws are steel.

I've got my plates off, and have new nuts (elongated tubes, hexagonal on the outside, about 1" long) but can't figure out how to make the nuts stay in their hexagonal holes in the trunk lid sheet metal. I imagine there is a special tool, but can't imagine what it might do to make the nuts fast.

This is so common that someone must have a way of fixing it without a special tool.