Description: only the end of the line curves right or left.
Use: this curve cast presents the end of the line and the leader around an obstacle. There is a current on the right (or left) that rules out a lateral curve cast. The less line you lay across the current, the more likely you'll get a drag-free drift. You want the line to fall straight between you and the obstacle. A 90º hook cast would foul the line in or on the obstacle.
Execution: with the rod tilted slightly to the right, immediately after the stop, snap your wrist to the right and back to the center to send a curve traveling along the line. It's got to get all the way to the end.
If it doesn't come out right, it's because...
Additional problem: to see when the fish takes the fly on the other side of the obstacle. Actually it's bound to take it, no matter what pattern you've tied on. That fish feels absolutely secure.
Solution: I don't know. This is a section on casting, not on extrasensory skills.