The company just got a new corporate acct with National and we will be switching over from Avis. I know about choose any car in the aisle but I can't picture how it works with a rental agreement, etc.

So you pick out the car and head for the exit - what happens? I assume you have to produce some sort of drivers license and National ID and then, do they print the agreement as you leave the lot? I'm sure it's simple, but I am just missing the mechanics of how it happens.