Wilderness permits, which are required for all overnight wilderness trips in Yosemite, are available at the Big Oak Flat Information Station, Yosemite Valley Visitor Center, Badger Pass Ranger Station, Wawona Visitor Center, or Hetch Hetchy Entrance Station. You must register at the station closest to your starting point. From November through April, wilderness permit reservations are not available. However, trailhead quotas are in effect all year, and quotas can fill up regularly for winter trailheads along the Glacier Point Road (including the ski area).