How do you measure fuel in semi truck tanks with a yard stick?

most times if you see a trucker measuring fuel with a stck, it is because semitruck fuel gauges are notorius for not being accutate it is esaier to dip a stick in tank to see what level the fuel is at. this doesnt tell how many gallons just the level I dont know what sort of crap trucks you have in the US, but in Europe most trucks are equiped with very accurate fuel gauges and computers to tell you the MPG and other information. Nobody ever uses a stick to see what fuel they have in the tank.