I was sceptical about this, I admit, but it’s actually really useful. Took me a moment to figure out where on the scissors to put it but once that was figured out it was incredibly easy and worked like a charm. You set the little black washer to the distance you want, then off you go. Very simple. I’ve always found marking seam allowances tedious and now I don’t need to. I write on the paper pattern that there is no seam allowance to remind myself to add it at the fabric cutting stage, so I remember to leave enough space between pieces as I’m laying out. I trust myself more with scissors than a rotary cutter so this little helper suits me well.