Right, first, they do not work in the directory... if you read the SDK ReadMe and crap, you would know this

And your best bet would be the talk to JohnWil, he knows most about the walls hack for the game before the SDK, so im hell sure he would know how to do it with the SDK.
BTW, Apoc said in the CCTV #1 that we would be able to enable them sleazy walls again, so... it must be pretty obvious to find them...