40% of trail quota numbers are held back (except for Whitney permits) for walk-in requests. Those walk-ins become available at 11 AM the day BEFORE the hike date.

Of the 60% that have been reserved in advance, those must be picked up by 11 (or maybe 10 AM) the day OF the hike. If the reserved ones are not picked up, they become available at 11 AM the same day.

If you go to the Visitor Center at 11 AM in Lone Pine, you will be put into the lottery, where everyone there pulls numbers, and they get to step up to a clerk for processing in the order of numbers drawn.