Originally tied by Hans van Klinken, the Klinghammer was tied to catch Grayling in the rivers of Norway. Today, this emerger pattern is one of the most used emergers across the world.
It's effectiveness lies in the fact that, like most dries will, it doesn't lie just on the surface of the water. The body breaks the surface film while the wing lies ontop. This magnifies the fly to the fish.
Fish on a long leader when either Trout or Smallmouth Yellowfish are feeding just below the surface.