 Pogo pins are tiny spring-loaded components, which allow the board they're mounted on to make momentary but electrically sound contact with another circuit. They're perfect for test jigs, when you need to perform the same QA test on an entire batch of boards. Position, apply pressure, and repeat. The type of board you're testing will likely dictate which type of Pogo pin you should use. The needle head Pogo is a good fit for small signal pads dedicated to testing. The cupped head can fit over small solder joints, such as the top side of a row of header pins. The somewhat intimidating spearhead works well for empty through-hole pads. And if you need additional stability or more contact with the test surface, the regal crown head may be a better fit.