Either the top cap of the atty, OR a metal driptip can cause a short, so it's a good idea to test your build after it's all put together. If you build on one of the box style ohm checkers, it's just a matter of putting on the top cap and take a reading. If you don't build on those, you can use a multimeter after it's all put back together by putting one lead on the 510 connection of the atty (the very center of the connector on the bottom), and one lead on the threaded screw-in part.