I have just tied a couple of these (Stimulator) in #12 & #14.

Two questions:-

1 Are they for river or still water.
2 How do you fish them.

Thanks.

Novice

Originally that was the Sofa Pillow, designed to imitate big stoneflies in the USA. It became the Improved Sofa Pillow and that was modified by Jim Slattery
... who in his youth played in the Stimulators..
into what we now see as the generic fly used on lakes and rivers.
I have had some fun with it on lakes and on rivers.
I usually omit the tail so it is just your average 'sedge'

Fish it dry, skated or static,
Killer fly,
cheers,

Roy

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C & R since 1963