You can probably read & run or scout everything but the Guardian in Upper Rockwood. It's tough to see the line in that one, even from above.
What it looks like:
River-wide hole with rocks that create a horizon line. It's the first major rapid once the rail goes from river-left to river-right, maybe 150 yards down from the tressle.
Here's the move:
Get in the last river-left eddy above the hole. Pull the hairy-ferry all the way across to river-right and run the drop up against the right wall. Total trust move.
The rest of the canyon is heads up 4+ moves, but the whole canyon bumps it to a V given the water level, cold water and the risk of swimming into the lower box. In all, one of the most spectacular canyons in the state.
If you're cashed from the 24 miles above - skip the Box for another day. It'll be there.