The metaphor of "rails" (as in "stripe is a payment rail" or "this board has a 5v rail") is interesting. I assume it comes from 3rd rails of railroads.
Where else is it used? What are the rules? Can I say "exhaust rail" or "water rail"?
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Ball boys/girls around a tennis court form a ball retrieval rail
The principle is that there's a resource at a guaranteed minimum distance away from any part of a spatially extended system
