Install Threads Almost Anywhere. You can set blind threaded inserts in sheet metal too thin to be threaded (minimum.02in. or 25 gauge grip length). Insert nuts have a flange on the outside. Tool pulls insert to form a bulge on the inside (like a rivet gun), sandwiching the sheet metal tightly. Great for installing mirrors on doors, assembling kit cars and street rods. Use bolts and machine screws where you never could before! The thread inserts in the kit are steel - aluminum inserts available separately. Kit comes with thread setter tool, 4 adapter mandrels, assortment of 4 sizes of steel inserts, and instruc.