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 be long. The variety of nipples and builds suggests the center probe (to unseat the driver at the correct moment) should be adjustable.
Sounds a lot like a VAR tool from the 60’s. But its adjustability required modification and it cost a fortune. But now we have the Problemsolver nipple driver. It is an empty pen with a set screw to secure a thin spoke section that serves as a probe. You can supply that piece from the center of any scrap butted spoke. We ship them with a 1.6mm hardened stainless “spoke.”
The driver is easily spun by hand or secured in a drill chuck for faster work.
You only need one, it can be adjusted endlessly. It’s perfect. Case closed.