FTS's Hair Stacker helps you to tie nicer flies. You can stack hair using this tool and after stacking it is easier to handle hair and you will tie better flies. Very handy if your tying muddler flies or hair wings. Stacker is very durable.
Just place hair into stacker and knock the stacker on the table couple of times. Then remove the inner part and hairs and you have nice, even bunch of hairs.