If you (like me) read the entire article without really getting an intuition for these "gauge blocks", here they are in action:
Machine Thinking: Origins of Precision and first project introduction https://youtu.be/gNRnrn5DE58
There's also a Cody's Lab video where he sees if they will wring in a vacuum: https://www.youtube.com/watch?v=jNEvS_bjKIo (using AvE's blocks)
You have a 'Master Set' of expensive Gauge Blocks that you use as a definite reference. Stacks of which can be combined with various tools for various purposes. https://i.ytimg.com/vi/2d-hGd_kYLc/maxresdefault.jpg https://images-na.ssl-images-amazon.com/images/I/61RhwssKaBL... https://i.ytimg.com/vi/n572qMo3g0A/maxresdefault.jpg
The 1 Inch block always seems to go missing.
[1] https://en.wikipedia.org/wiki/Coordinate-measuring_machine