The FAB or ‘Foam Arsed Blob’ features a foam tail which raises the butt of the fly – this when combined with a retrieve gives the fly a twitchy motion in the water and is deadly for attracting rainbows.

fish on a sinking ,intermediate , line with a long slow pull leave for a few seconds so the fly floats up then pull again ,or try fishing it on a floating line as an atractor fly , or fish it washing line style with buzzers suspended from it