How are people able to spray paint the side of overpasses?

I was driving under one today and couldn't figure it out, unless they repel.How are people able to spray paint the side of overpasses?
I'm guessing they lean over the edge, probably have someone hold thier feetHow are people able to spray paint the side of overpasses?
for one they have no respect and some of them are even stupider and they climb on things and take daring risks. idiots
On the M25 around London, there is a very tall rail bridge (we're talking the height of a 6 or 7 storey building). On it is written the word ';peas'; in metre high letters.





It really makes you wonder, doesn't it.