If you need to keep your Fetch vehicle longer than your original reservation, no problem!
When viewing your current reservation through your Fetch account, just look for the "Extend Rental" option. If your vehicle isn't already reserved, you'll have the option to extend your rental on an hourly or daily basis. Once you complete your rental extension, your new return time will be updated within the app.
However, if you aren't able to extend your reservation, that means that another Fetch renter has reserved your vehicle. You'll need to return your Fetch truck on time in order to avoid a $30 late return charge. (Your on-time return ensures that other Fetch renters are able to begin their reservations on time.)