So I was doing something totally unrelated to anything I’m about to show you, yet I managed to figure this out. It’s pretty simple but its not very practical. I mean, it takes like 6 or 7 minutes to actually do it in game, which would mean you’d totally get owned in the ass in verses if you attempted it (anyone up to that challenge? send me a video of you doing it in verses mode and I’ll post a picture of my tits).
Anyways, I first tried it with the boxes, but they weren’t tall enough and I kept breaking them 
Then I tried it with the hand jack, and it was barely not tall enough. Then I managed to flip the hand jack over, which was then too tall to jump on. So I had to reset the campaign again (this time not breaking the boxes) and use the boxes to jump on it. Easy enough? Sure it is, but the fucking bots like to get in your personal space so I’d recommend doing it with friends or kick the bots. On to the video!
Edit: I know it doesn’t make sense to do it, but in my defense I was trying to get the no medkit achievement ON EXPERT and spending all that time to save a little health would really help in the long run! AND NO, ZOMBIES DON’T SPAWN IN SINGLEPLAYER WHEN YOU’RE DOING THIS… I HAD NO CHEATS ON WHILE DOING THIS!