3 hours (nobody really knew the steps, we took our time), my first try ever.
Unlocked at round 15
I was watching the last zombie every wave. I didn't do much for the achievement. At one point, I held the last zombie at a window for 10-15 mins, and I got steel barricades.
COD4 10th Prestige 55. My favorite COD.
Last edited by BR247; 03-17-2013 at 06:16 AM.