Backup Car Rental Reservations
 

I've seen this mentioned a few times, can anyone explain the steps and how this works?

Obviously want to avoid any additional fees or charges.
What would one need to watch out for when doing this?

There's no penalty for no-shows unless you prepay. I usually make the backup reservation an hour later than the main one so I can cancel it if I don't need it. You won't be penalized if you don't cancel it but you don't want to abuse the system either.

Thanks, I'll try that for my next trip.