I would direct you to the thread that tells how to do it, but I will spare you from that because I think you might of already read Forging 101. What I would do is that I would take a few single boxes and surround the wall with them. Then take two doors and put it in top on one side then on the other side and let them sink in. Grab the wall and it should do what you want it to. You might need to try a few times before you actually get it. If you need help refer to the Forging 101 thread. Good luck.