Yeah, I'll give it a try.
So you touch off with your tool on to the gauge. When the light goes off you look the quill. Then you know you're exactly two inches for the work. Moove the knee up accordingly.?
Use one like all the time to zet my Z-Axis Zero. While I am using a CNC, I don't see why it is not just as useful to set the Z-Axis zero point for manual operations as well.