The climbs on this boulder are near vertical. Further, it features some of the better rock quality at Rancho Penasquitos.
This boulder lies at the western section of the waterfalls, on the southern side of the river. When approaching the waterfalls from the main trail, head left, down the stairs, and across the river. The boulder sits to the right, with the climbs facing north.
Browse More Classics in Thumb Boulder
Mountain Project's determination of some of the classic, most popular, highest rated routes for Thumb Boulder:
Hangnail Left V2 Boulder, 8 feet
Hangnail Right V4 Boulder, 12 feet
Featured Route For Thumb Boulder