First time seeing it. I did see on a site a quilter's plumb line chalk marker. It is just like the carpenter's chalk line but comes with iron off chalk. I think it was a on a Pellon site? I though it would be awesome for squaring up quilts with. She had a video showing how to use it to mark crosshatching on a quilt top too. I didn't order it but I am hoping it will become available at my LQS.