These very large boulders (more like small flatironettes) frame the Royal arch trail as it makes it past sentinel pass. (top of the switch backs before you drop towards the arch)
The East Sentinel Boulder is some 100 feet East of the pass while the West Sentinel boulder is the rock that forces the trail to drop and go around. Both "boulders" provide exciting routes to their summit.
Getting There
Hike the Royal arch trail to the top of sentinel pass. To reach the base of the East face of the West Sentinel Boulder continue past the pass and down the wooden steps. Look to your right for a severly overhanging rock with a notch and a large pine tree to its left. East Sentinel boulder is left of the pass at about the same level as the pass.