at ORD, when you go through the premier security, you can see the passage way to the left of the TSA pre station.
Now, one time, at the premier line, the lady said the line looks long and they sent me way down to the left to a security area I never saw before. I went through very quick because no one was there, then exited into the terminal on that side. Not sure what that was. I had assumed that was a special GS area