Nothing. I had no interaction with the Avis staff. They were closed.
The rental counter could have been open. My flight arrived just after 2PM on a Monday. The other car rental counters were manned and open, but Avis had apparently closed promptly at 2PM. Since the airport is a relatively small one, I initially had few options for a ride. There are no taxis and the other rental agencies had no available cars. I called my brother-in-law, who lives an hour away, to come get me. I was fortunate that it was a holiday. He was available to come get me immediately. Another rental agency (Enterprise) fortunately had an unexpected vehicle available which I was able to subsequently rent, but it was expensive. I paid more for one day of car rental than for my flight thanks to not being able to keep my advance rental arrangement with Avis.