Building wheels is a sweet rhythm if you have parts that fit and tools that work. Tightening nipples when the wheel is still loose requires some way to make each one equally turned.
Eldi offered a Yankee-style tightener. Bicycle Research gave us offset screwdrivers. The advent of deep rims means your tightener must often be long. The variety of nipples and builds requires the center probe (to unseat the driver at the correct moment) be adjustable.
Now we have the Problemsolver nipple driver. It is an empty pen with a set screw to secure a thin spoke-like probe. We ship them with a 1.6mm hardened stainless spoke.This thin diameter makes the tool much easier to use.
The driver is easily spun by hand or drill.
It can be adjusted endlessly, it’s perfect. You need one. Case closed.