For this you will need to play on the mission Embedded. Best to pick Recruit Difficulty.
Towards the start of this mission you will pick up a cinder block in order to progress. Make sure you do not pick up a different Cinder Block, you also need to carry it with you throughout the mission until you get to the end. You are allowed to drop it to take care of enemies.
Then get the end of the mission as normal with the Cinder Block when at the end with the cinder block in your hands simply press
on the ladder and the achievement will unlock.
If you are still struggling, then feel free to use this as a reference.Call of Duty: Modern Warfare Companion Block & Play Dead Achievement Guide