Plants vs. Zombies Garden Warfare

When playing Gardens and Graveyards as the zombies select the engineer. Once in the game head to the teleporter build site. If the teleporter is down or hasn't been built yet it will be marked with a Purple Wrench. Otherwise using the holographic door will teleport you to it. Use your jackhammer to hurry there. Around the teleporter is 3 yellow scrap piles. Run up and hold B to build the turrets. Once built you can also upgrade them to Mark 3 to protect your teams teleporter.

Also as a note the turrets count as raising zombies for the summon 5 zombies achievement. So if you do this right away you can knock out 3 achievements at the same time (Build 3 Turrets - Summon a zombie - Summon 5 zombies in the same session)