Hopper
Foam body, rubber legs, and a profile that says terrestrial without specifying which one — a surface pattern built for versatility. Fish it as a dry on rivers or use it as an indicator with a nymph dropped below. Its buoyancy is remarkable, it lands with a satisfying plop, and trout take it for everything from a beetle to a grasshopper.
Fish it during summer and autumn on river. Use it when the naturals are about and fish are feeding seriously. Have it ready for selective moments.
It works because the profile reads as terrestrial hopper or general leggy surface insect. Straightforward pattern, proven result. Fish it with confidence when other flies don't move them.
Starting points, not rules — depth, presentation and size usually matter more.
Try black, Bibio or claret under cloud, in a ripple, or over peaty water. Use ginger, tan or amber in sunshine and when matching natural terrestrial insects. Bright foam helps you track the fly, but on flat, clear water a subdued body can be less alarming.