These adjustable gaps serve three purposes. They:
1: allow us to vary the test parameters when necessary.
2: add to the capacity of the Octopus Test Bench's annular test gaps for testing up to 14 cylinder magnetos.
3: can be moved along the rod to alter the spacing between the test gaps - needed when testing a bunch of HT leads when they are housed in a metal tube, each lead exiting adjacent to it's spark plug on the engine