Rivnut's
 

Rivnuts

When you need them, they're great, better than simply tapping a few threads into something and far more convenient than welding a captive nut somewhere.

Hand Rivnut tools, while good, can be difficult or near impossible in tight spots and can just generally be a PITA. And will run you $50-150 depending on the quality and mandrels.

Power adaptor and pneumatic Rivnut tools will run you $90-200.

So... Here's a YouTube link for a DIY solution that will not only fit into tighter situations, it will fasten the Rivnut more secure, can be made for ANY size Rivnut and will only cost $1.00-2.00 per mandrel size.

This is genius: