Navegator:....EXACTLY.
Fun fact: some years ago when the Church Parish I belonged to was healthy and growing our pastor was.. not so healthy and dying (old age will do that to you) he was on Oxygen.. When the bottle ran dray they had to change it.. Turns out I was the only one present who knew how to do that (Though I do admit it had been like 40-50 years since I'd changed one)... Amazing what you can remember when needed. Got it changed.
I would have thought his assistant would have been trained in how to do that (and thankfully the procedure is rather obvious).