When I was growing up in the UK the convention for construction projects was always to put the power source explicitly on the circuit diagram with a symbol and a label, e.g. "9 V battery". Not only would this make the power rails clear, it would also give an indication of the expected power source when building it.
I see the use of "voltage rails" and "ground rails" as a convenient shorthand for engineers, but it doesn't always aid reading comprehension.