Your sentence is a bit ungrammatical. It would be more natural to say "À quelle heure le garage ferme-t-il?" if you mean "when does the garage close?" (expecting a precise time: it closes at 9PM), or "Quand le garage est-il fermé?", if you mean "when is the garage closed"? (expecting an interval: it's closed from 9PM until 10AM the next day).

I had to look it up. That's a very useful sentence... ;-)

s/la/le/