Despite the naughty-sounding name, a diddle stick is actually just a small non-conductive screwdriver-like tool for making fine adjustments to components inside a variety of electronic devices.
Yes, it's supposed to be small.
Diddle stick may be hyphenated (diddle-stick) or combined to form one word (diddlestick).
Engineer 1: Crap! I got my diddle stick wedged inside the gonkulator housing again!
Marketing Drone: What were you doing with... never mind; I don't want to know.
Executroid: Ewww! I'm never touching the gonkulator again!
Engineer 2: Hee! They have no idea what a diddle stick is, do they...