It’s not much of a stretch to say that without nuts and bolts, the world would fall apart. Bolted connections are everywhere, from the frame of your DIY 3D printer to the lug nuts holding the wheels on your car. Though the penalty for failure is certainly higher in the latter than in the former, self-loosening of nuts and bolts is rarely a good thing. Engineers have come up with dozens of ways to make sure the world doesn’t fall apart, and some work better than others. Let’s explore a few of these methods and find out what works, what doesn’t work, and in the process maybe we’ll learn a little about how these fascinating fasteners work.