I'll often use this technique when I'm expecting a hatch but the bugs haven't started coming off the water, or when the hatch has started but not many fish are rising. It's also a great way to survey a trout stream. Fish the water in roughly 3-foot-wide stripes, so virtually every trout in the river sees your fly. This way, you can cover vast amounts and types of water, stopping only to go around logjams, beaver dams, and other fishermen. The method works especially well in faster or more broken water. Fish don't see the fly coming-it's just there and gone in a second or two, and they'll often grab it out of pure instinct.