What are the different ways of measuring the pitch diameter of a screw thread?

[Silverbullet]

I have a set of triangles which fit on the micrometer. I had some weird threading job forty years ago , I was going to buy the wires but these were easier to use and the job passed inspection so I guess they were done right. Anyway they cost a bit more but the ease of use made up for it. Don't even know if they still sell them . Pretty sure they worked for any 60 degree thread.