Once a wheel is laced, the nipples must be turned down equally. Only then can truing and tensioning begin.
You can simply count threads showing outside the nipple entry or employ tools by Eldi, Var, Bicycle Research, Cyclus, or Problemsolvers. You can even make your own.
Today we offer exquisite drivers by BSC. These stainless bits match nipple ends (slotted, square, or hex), have a set screw to adjust 1.6mm pins, and include spares of each plus a Wera 1.5mm allen key.
The driver is easily spun by finger, hand, or drill.
What a magical time to be a builder! Tools like these were only a dream before 2021. Thanks and kudos to Dave Gunthorpe at Bicycle Service Centre in Wales.