Birks, which is itself a satellite of St Sunday Crag, resides on a southwest to northeast ridge. Below the summit and about halfway down the main slope, a level spur juts out eastward and then curves around to the north to run parallel with Birks. At the far end of this subsidiary ridge is the rocky summit of Arnison Crag. The slight col where the Arnison Crag ridge connects to the flank of Birks is Trough Head.