Wouldn't that be called a "reservation"?
It's similar - Outback doesn't do reservations - they do call ahead seating, where you can call and they will try to have a table ready for you in 5 minutes or something like that. But you have to call 2 hours from the time that you want... I think that's the time frame anyway. So if you know they'll be busy then you can call around 4 and tell them you are coming around 7 or whatever... we've used that a few times and have always been seated within 5 minutes of showing up.
We also like to call and put our name on the waiting list - especially when we know we want to go but still have to get ready/finish chores/whatever. It is really nice for those times when you don't really know 2 hours in advance where you want to eat (I don't know about most people, but we usually don't plan 2 hours in advance, we just decide on the spot that we want to go out and eat that night). What they do is just put your name on the list when you call, just like if you had walked in the door - but you have to make sure that you are getting ready to leave when you call because if they call your name and you aren't there then you just have to put it in again. I always ask what the wait is, and if it is less than 30 min. then I don't put our name in.
Sometimes the hostesses are a bit confused though - they keep two seperate lists sometimes and pull a name from the regular wait list then pull a name from the 'phone call' waiting list. I've seen them ask people when they come in if they called to put their name in, clearly confused - and people sort of smirking and saying 'oh, why yes we did call' then the hostesses put their name on the short list and they get called quicker because of it.