Plenty of folks know of the tool called a tap. They make threads in holes for the bolts that hold signs and engines together and they’re very common tools. The process works like this: first a hole is drilled with the correct size drill, after the hole is cleaned and checked to be the correct size, a tap is rotated into the hole at a speed and rotation that matches the threads of the tap. Boom, you’ve got somewhere to put your bolt. There are other tools that are used to tap holes, but they’re the kind of taps that only work when used in a CNC mill. They are called thread mills and can have as few as one or as many as hundreds of teeth. Thread mills are used in difficult to reach places or in hard materials like titanium. They spin at thousands of RPMs as they rotate around the thread; it takes a computer to put them in the right place at the right time. At the end of the process, it takes a trained eye to distinguish the threads made by one tool vs. the other. Next time you tighten a bolt, remember there’s more than one way to tap a thread.