We have adopted the use of key lockboxes with great success. If you arrive late, if your flight is delayed or early, if you want to pick up a car or shop for groceries -- you have flexibility without worrying someone is waiting for you to give you a key.
The lockboxes work very easy, just punch the numbers in any order and the mechanism opens, you pull it open and the keys are inside. If you mess up press clear and start over. They work flawlessly from what we can tell.
When you depart from your trip — lock the doors to the rental, open the lockbox, put the key in, close the cover (it locks automatically), that's it.
We provide you the code when your rental is paid for and also at that time we give some simple neighborhood driving directions and suggestions where to park, unload, etc.

The lock box, if for some reason it has too many keys pressed it can sometimes not work, you just press “down” the reset button (marked “CLEAR”) in the middle bottom portion it is sort of triangular shaped, that starts it fresh or “clears” it.
When you press the code in (any order works) you push down (and keep it pushed down) the top middle button (marked “OPEN”) and it releases the lock bolt. This can be tricky if you release the button it will set the bolt again — so just hold that button as you let the front fall back and out of the box (into your hand).
When you have removed your key, if you did not hold the top middle button it will have set the bolt as locked. If that happens, just dial the code, hold the top middle button, insert the front into the box and release the top middle button and it is locked again.
Sounds complicated but it is like anything else, if you break a simple action into steps it will sound complex when it actually is not. But of course before you have experienced how it works it can be intimidating.