If you’re lucky, the fasteners that you want to safety wire will be pre-drilled, but if not, it can be a bit tricky ventilating hardened steel. Enter the Nut Saf-T-block by MTE Industries. This incredibly simple, yet effective widget lets you drill safety wire holes through the head of bolts or nuts across the diagonal. It’s designed to accept up to ¾-inch bolt heads or nuts. Just place the fastener in the “V” grove, tighten down the set screw, drill, and deburr. At around 30 bucks we can’t think of a reason not to have one in your arsenal of tools.