This is a shuttle hike from the Tom's Thumb Trailhead to the Thumb and then down into the Gateway Trailhead.
It's easier to hike down from Tom's Thumb than up from Gateway, but either direction works.
The first section up to "Tom's Thumb" is the most challenging part of the hike. Continue on the "Tom's Thumb Trailhead" until the first sign directs you off to the right (north) to the Thumb. After visiting the Thumb, backtrack to where the East End Trail intersects the Tom's Thumb Trail and heads south. The trail is (as of 2014) very well marked.
From there it is downhill until the trail crosses the Gateway Loop Trail. At this point turn to the west (right) and climb up to "Inspiration Point". This is the second major climb of the hike, but not nearly as tough as the Tom's Thumb initial ascent. Once past "Inspiration Point", it's mostly downhill to the Gateway Trailhead.
Water is not currently available at the Tom's Thumb Trailhead, but restrooms are open. Water and restrooms are currently open and available at Gateway.
Check out the Official Route and Triplogs.