This is a cheat for High Rise.

When you enter the match go to the left of the map and walk to the downed scaffolding.

Try to jump on the side of it and use it like a ladder, it might take a minute.

When you do get it, walk across the ledge until you get to another tilted bit of scaffolding.

Then walk up it and jump up onto the roof and you are all set.

Make sure you have a sniper!