-At least two people are required for this glitch. Make a match with two slots and a private slot--this is possible with any amount of people. Invite a friend and send him a private chat invite. Ask him to meet on the roof of the spawn where the fast roping skylight is located, then have him stand in the middle between the air conditioner vent and the ledge on the far left of the entrances to the roof. Hold L2 +Left Analog-stick Up in front of the vent, then release L2 and keep holding Left Analog-stick Up. Release Left Analog-stick Up and you will be on top of the vent. Walk over your friend's head. Note: Your friend must be crouched. You will be on top of the ledge of the roof. After you are on the roof, make a right and go forward before making another right until you reach the middle office room. Stop, align yourself with the left edge of the small building, jump off, then walk in a straight line until you reach the end of the path. Turn to your left and you should see the overhead of the left catwalk/bridge. Align yourself with the edge of the overhead, then walk forward. You should be on top of the overhead. Proceed straight until you are at the edge of the overhead. Align yourself with the low concrete wall, then jump off. Follow the low wall until it ends by the stairs. Align yourself with the low wall below the edge near the light post, then jump off. Turn to your right where there are an abundant amount of plants and trees, then walk toward them. Keep walking on the sides of them. With the correct camouflage you can hide form the enemy and attack when they are close.
-Go to the roof with a partner and get in cover on the box on the right of the roof. Look up all the way with your weapon also pointing up to go on top of the box. Have your partner stand to the left of the box, crouching in the middle, then walk over your partner and you will be on top of the roof. You will now be free to walk around out of the level's boundary.