I was just reading about this in a quilting book. The explanation goes something like this: the line of stitching takes up some room (even if it is only a very small bit) and so that it doesn't take up room "within the block" you sew a scant 1/4 inch so that the line of stitching is taking up room in the space between the 'block' and the 'seam area'....Is that clear as mud :lol: ?