Cute little GPIO buffer boards. So that when I start wiring up electronics components in a circuit to my tiny and overpriced and perpetually out-of-stock SBC (single board computer) that took forever to arrive, for a project I am working on, I don’t accidentally turn said single board computer in to a blue smoke generator because I wasn’t paying attention, or had a connection go awry. No matter how much I earn, I still feel stupid when I blow up a $40 part because I didn’t check my circuit properly, or had a dab of solder in the wrong place.