Downstream of every rock are three obvious seams: the left seam, right seam and the slower seam in the middle. That part is easy. But the most productive seams are more hidden, and many anglers seem to miss them altogether. These are the two merger seams, where each fast seam meets the slower part in the middle. And if I had to pick just one target area, day after day and season after season, I would surely choose the merger seams . . .