Here's the response from Nancy's Notions when I asked about a video so that I can understand how the blind hemmer does quilt binding. I can't capture the image that was in the email but if you go to the webpage on Nancy's Notions for the blind hemmer, the picture is there.
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Thank you for your email.
Our staff is planning for a video. But it may be a while before it can be completed for viewing. Below, I have an image that is included on our Blind Hemmer webpage of a sample of quilt binding done with the blind hemmer. Our sample doesn’t include the corners. On the blind hemmer machine, the needle comes in from the left side. So, for the mitered corner, as long as it is folded, you would only catch the edge of the long part of the binding, not of the miter itself. Also, you are only catching the backing and maybe some of the batting, but you aren’t catching to quilt top.