This achievement is obtained during the Chapter 3 level when you are trying to escape the POW camp as Karl. First, fix the showers and retrieve the suspenders, which can then be traded for a first aid kit with one of the soldiers on the roof of the sausage house.
Then head to to the laundry house. Give the first aid kit to the sick soldier, and when he can walk again, he'll drop the laundry bags down into the cart that is there for you to push. Simply stop the cart under each of the 3 laundry bags, and this achievement is yours.