This location works either way you could be in any teams red or blue team to place the turret.but the location is closest to the blue teams flag. You know that truck that's open so you could go through it? (this place is in somewhere near the blue flags team,not red team). There a certain spot.go inside the opening and in the left hand corner place the turret there.and there it's invisible.if you look at your map,it shows that theres a turret but when in the main screen you can't see it.
To do this glitch throw a Concussion or Flash Grenade at the wall so it bounces back at you and stuns you. This will count as deflecting an explosion for the Blast Shield Pro. This only works with the unpatched version of the game.