The message above is a little misleading in saying they had "sold" all the fast passes in an hour, as you don't pay for a fast pass.
Assylum Gal : The fast pass system works in the following way. On certain rides where they use the "fastpass " system you will find 2 entrances to the ride. The "standby queue " where you just queue for however long it takes to get on the ride, or the "fastpass queue", either beside the ride or at various places in the parks (check your guidebook for details of locations) you feed your park entry ticket through the machin and it will give you a 2 hour alloccated time slot for later in the day. You simply return to the ride any time within that slot and go straight into the Fastpass queue which will save you too long a queuing time. Above the ride where it tells you the approx queuing time there is a display which tells you what time the faspasses are currently being issued for, so you can decide on your best course of action.

Babblin Boo