Rock: No routes yet. A promising looking cliff at about GR333770 can be seen from the creek on the West side of Sentinal.
Alpine: The easiest ways up Mt. Sentinal are to slog up the bowl on the North side of the Mt. Elliot/Sentinal col with a couple challenging bits of scrambling higher up. This route is also the easiest descent. Alternately walk up the Cline River a ways then follow the NW ridge to the summit with some short steps (FA: B. Hart, O. Miskiw, 1975).
North East Slabs(grade unknown) - Mike Adolph and partners established a tough route somewhere on the clean triangular slabs in the sentinal/elliot bowl. Slabs visible from the highway. No further info.
West slabs - Fun scrambling can be found numerous places on the rocky West face of the peak accessed via Cline River and a tributary on backside of peak.