I recently built a pour-over coffee maker that used hanger bolts in the top piece to make it adjustable for filling large and small mugs. To screw the hanger bolts into the top piece, I thought about using pliers. But I didn’t want to clamp the jaws of the pliers onto the bolt end, as it would ruin the threads. Instead, my coworker gave me this great hint. He showed me how to lock two hex nuts together to create a temporary head, so I could then use a nut driver or wrench to screw the hanger bolts into the top piece of my pour-over coffee maker. — Jenny Stanley
This bolt head hack will work for more than just hanger bolts. You can lock two nuts together to make a bolt head on almost any threaded rod.