Two possible locations of the Ford of Carrock²

The Carrock was large rock that stood in the middle of the Anduin's stream, some twenty or thirty miles to the north of the Old Ford on the way to the Forest Road through Mirkwood. From the eastern bank of the river, a well-maintained ford led to the stony island, and a set of carved steps climbed to its summit. As late as III 2941, when Bilbo and his companions came to the Carrock on their journey to Erebor, the crossing from the western bank to the rock was impassably deep and turbulent.

In the following years, it seems that the Beornings had extended the eastern ford across the entire Anduin at the Carrock. In the closing years of the Third Age, at least, the descendants of Beorn were said to keep the Ford of Carrock safe and open, though they charged high tolls from travellers crossing the river.

In the index to Unfinished Tales, Christopher Tolkien proposes an alternative interpretation: that the 'Ford of Carrock' across the entire Anduin was not the same ford as that described in The Hobbit, but was actually a reference to the Old Ford some twenty miles to the south. This explanation fits the established geography rather better (the Old Ford was already a complete crossing that lay on an established route) though on this interpretation, it's difficult to account for the transposition of the name from the Carrock itself to another ford many miles away.