Hallin Fell stands like a plug in the outlet of the Martindale valley system. The outflows of Rampsgill, Bannerdale and Boredale are deflected west around the fell, eventually finding the shore of Ullswater at Sandwick. Fusedale and the little valley above Howtown drain around the east of the fell to meet the Lake at Howtown Wyke. The southern boundaries of the fell are therefore easily defined by these watercourses and the Howtown to Sandwick road with its ferocious hairpin climb to The Hause.