Just to prove how old I am. When I was a kid and delivered newspapers on my bike, a single speed heavy duty monster, I carried a spoke wrench in my pocket and a little bag with a universal wrench and spare front wheel bearings. The spoke wrench was about the size of a silver dollar with a groove cut into it and would tighten most any spoke anywhere. They were free at the Western Auto or Pep Boys, all you had to do was ask someone in the bike department and buy lots of front wheel bearings.
When my Crystalyte 5304 kit was delivered and after I had assembled everything I had this funny looking thing left over. It was in the box with the charger and I tried to fit it on the charger, controller, handlebar, just about anywhere that was round. Didn't fit.
After a few days riding the bike the spokes started making lots of noise and kept getting worse. Along about that time I found this forum and noticed a member complaining of loose spokes so I knew I wasn't along.
The very next day I stopped at my LBS and asked for a spoke wrench. Since the store was full of toys I neglected to look where the clerk picked one up but paid attention when he wanted $7.95 plus tax for it. Laying on the counter it was a round object, about 3/4 of and inch thick, shiny cheap chrome and except for the chrome part identical to the thing I still had in the charger box back at the house.
I thanked him for his time, told him I'd make one and wouldn't spend the $7.95. I lied about the making one part. Now I carry it in my tool kit on the bike confident I can find it as I know what it looks like.
Fortunately after several weeks (knock on wood) the spokes quit loosening every day and I haven't had to tighten them for a few weeks.