No special access issues
Both Supercrack and the Black Rhino boulders sit above Aberglaslyn Hall; a former LEA education centre now currently unoccupied. However were ownership to change hands, access may change.
Park on the small layby by the bridge towards Nantmoron the road between Beddgelert and Porthmadog. Cross the road (carefully) and take the path leading up into the woods and above Aberglaslyn Hall. Follow this through a gate, weaving up the hillside until a wall can be seen trending across the hill above you. Reach the wall and turn left, following this over interesting terrain until a stream is crossed and a hillock appears above you to the right. Head towards the top of the hill but trending left slightly to a plateau. The crag will appear on the right.