I purchased at my LQS a seam ripper that looks like a mustach trimmer. I love it and use it very often. It is so fast and easy to use. It cuts the threads only and not the material. You run it between the two sewn pieces of material and it cuts right through the thread.
Small trimmer made by Wahl
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Run it between the two pieces of material that you need to rip the seam out of.
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