Pretty simple in theory, but I did find it to be a little buggy and unlocked it on my third knock down.
Find a door, sprint towards it by clicking in
and then as you get to the door hold
to slide through it.
Hopefully there will be a guy close enough on the other side for you to knock them down and pop the achievement.
Should be able to do it anywhere on a case really, but can be done easily by going to Quick > Operation and setting it to easy difficulty