i park in an outdoor attended lot, not a garage, but same idea. we have monthly parkers and day/hourly parkers. pretty much the monthly people are allowed to go park themselves in the back rows, and the daily people need to leave their keys with the attendants and then they tetris them in like 4 cars deep, and the day parkers are supposed to notify the attendants that their coming to get their car about 20 min in advance so they can tetris it. i have never not gotten a spot in my lot. worst comes to worst i leave them my key and they tetris me. hardly ever.