i really love this, but im not sure what triggers the wall in the second level. id love to play more but im stuck.
There are two big buttons in front of that wall, and the dialog pop-up instructs you how to lead your fellow workers right then. If you stand on one button and right click near the other, the workers will run over there and stand on it to trigger the wall. Or aim and hit left trigger if you are using some kind of gamepad.
Sorry it took so long to notice your question.