Yes, I've read all the other posts and I still don't get it. Dumb it down for me.

Arriving from DFW on AA, connecting to BKK on JL.

It's my understanding I don't go through immigration or customs, but I do go through a security checkpoint. Where is this checkpoint? Are there signs? I know I stay in Terminal 2 and this should be easy, but for some reason it's not.
http://www.narita-airport.jp/en/guid...ter/index.html

I've flown into NRT a half dozen times, but have always terminated there, so I just can't figure this connection thing out. I'm racking my brain trying to remember what direction and where all the connecting people on my flights disappeared to and just can't.