Can someone please walk me though what will happen when we arrive from the US in Frankfurt (UAL) and then transfer to a Lufthansa flight to Rome? I understand that bags will be checked through to Rome and that's where customs will be - but I'm not sure if I've got FRA figured out. How will we know where to go for a transfer to another Schengen country and I assume Lufthansa and/or Schengen is in another terminal? I've tried looking at the FRA website but I'm still concerned we are going to walk out of the airside area and wind up in the wrong place. We do have 2 hours layover which I hope is enough. Thanks for any insight.

Monitors/ displays will give you the gate number of your connecting flight once you get into the terminal building.
Even if you have already been given the gate number of your connecting flight to Rome, double check on the monitors upon arrival.
Follow directions for "Transfer" (instead of "Exit/Baggage Claim&quot.

I don't think you can leave the airside part of the terminals accidentely because you will see warning signs at the exits to baggage claim that you are about to pass a "point of no return" (and would have to proceed thru security again to re-enter).

If you exit you'll simply have to go through security to get to your gate. It's not a big deal.

I routinely connect through FRA and if it's a long layover (which 2hrs is in my book) & will sometimes exit just for grins.

I believe UAL shares a terminal with LH, so you will likely arrive on Level 2 and depart 1 level lower in the same terminal. QED.

In practice you don't go through Customs anywhere. You go through Immigration in Frankfurt. Your checked bags will carry a tag that - if there were Customs officials at Rome, which there almost certainly won't be - will identify them as having originated outside the EU. Which doesn't matter because even if there are Customs officials at Rome, they won't check your bags.

There's no reason for changing terminals in Frankfurt.

Transferring in FRA is pretty easy. Signage is very good. As others have said check the monitors for gate info. You shouldn't have to leave terminal but will go through passport/immigration (sometimes twice), but not customs. You may have a long walk. FRA is very spread out. Last time we transferred there, we were also going to FCO (though on LH for the whole trip). Layover was a little over 2 hrs and we had lots of time to kill.

Thanks everyone1