That is CDC and not marabou. It's the same principla as Marc Petitjean magic tool. It's not for marabou as your thinking of it. It's for flies mainly. Not only is it not for marabou, what it would do is line up the feather barbules at the stem and for marabou to be done right it's lined up more by the ends. When I stack my marabou I just keep the tips close to the right length and then after I have enough (which mush of the part that is cut from the stem are staggered) then when you pinch it all together you have to pinch it near where the shortest ones are so you can then cut that end to tie it natural looking jig tail.

That kind of tool is for using dubbing loop and then palmering the feathers on the hook using that twisted dubbing loop to hold them all together.

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