Radiator - which way is up ?

[IainRR]

I've had a new tall upright rad delivered but it's been marked with a "top" sticker at both ends !! How can I tell which is actually the top?
One cross pipe is completely open from end to end, the other has a constriction half way along with a small hole in it. Should the constricted cross pipe be a the bottom so that water takes the path of least resistance and moves up the rad, across and back down ?

thanks
IainRR

 

[seco services]

Should the constricted cross pipe be a the bottom so that water takes the path of least resistance and moves up the rad, across and back down ?

thats what i would go for.