This is one of my favorite tools-the Thread Setter, aka the Nutsert. It's a sweet set of pliers and threaded inserts that can be inserted into sheetmetal to provide a backless attachment point in a blind hole. By inserting the knurled insert into the appropriate-size hole, you can add an attachment point for anything you can dream up. This is especially handy for attaching brackets and parts in hard-to-reach locations where it's impossible to put a nut on the backside of the part you are trying to secure. You can buy the Thread Setter and other similar tools for about 100 bucks at your local hardware supplier or tool truck. Check it out.
1.The Thread Setter comes with several different-size inserts for bolts between 1/4 inch and 3/8 inch. An oversize drill bit is used to drill a pilot hole in the metal for the insert. | 
2.Next, the appropriate insert for a 1/4-20 bolt is threaded onto the end of the Thread Setter tool until the shaft of the tool bottoms out into the end of the insert. |
3a.The tool is then inserted into the hole we already drilled. Making sure the insert is sitting flat in the hole, the handles are squeezed together, which compresses the insert in the hole. The knurled edges of the insert grab onto the edges of the hole, preventing the insert from coming out or spinning in the hole. | 
3b.The tool is then unthreaded from the insert. |
4.And now we have a threaded hole with a perfect 1/4-20 thread inside. We put three more inserts in the chassis of our '67 Chevy and mounted our fuel cell without any nuts. | |