This screwed over so many gamers. Took me a good half hour to realize what you have to do. The game mechanic is, there's rockets that can go through the portals to hit something else. There's also an air duct that you are supposed to get to, but it's too high to jump to.
HINT: Look around the room with the duct. See if you can spot something that would easily break from a rocket shot.
SOLUTION: Fire a rocket at the glass tube. A cube will come out of the broken pipe. Stack the cube in front of the duct and leave.
ALTERNATE SOLUTION: Stack chairs like a man.