In order to perform this glitch, you must play until you reach the point where you have saved the Marines under siege by the Wraiths. Make sure you grab a Ghost during the fight. When the doors open and Corporal Perez comes out, drive your Ghost up the stairs. Wait for the Scarab to pass and then go all the way up to where the Scarab stops. Knock the boxes off the edge and clear the deck of the Scarab. Back all the way up to the wall and boost onto the Scarab. If done correctly, both the player and Ghost should be on the Scarab's deck. Now carefully drive up to the top of the Scarab. You should get to a point where you cannot move, even if you boost. It does as much good as a turret. If you get off, the Ghost will turn until it is facing forward and will still hover, but without the light that normally comes with it. The exact same thing can be done with a Warthog, but it might take a few attempts. When using the Warthog, back it up into the building to the far back, and from there drive it up the stairs. Note that you may need to melee the turret on the way. Or you can use the Sputnik skull and melee the boxes out of the way.