Technically a tool, even if it's disposable.
I've seen too many people baffled by setting up ignition timing over the years, playing all sorts of games with measuring piston movement and using specialty timing plugs and crazy schemes.
I find a part that rotates with the crank and do it the easy way. Fuck trying to figure out cryptic timing wheel marks or getting oil in the face.
If you don't have a degree wheel, you can make one in two minutes with a sheet of paper.