Some machines, including my Bernina have a place on the bed of the machine to screw in a metal "seam guide" which can be adjusted to the width of seam you want. The edge is about 1/4 inch high. But the ruler is a good idea and less expensive than my accessory seam guide that was pretty expensive. I don't do other than a 1/4 inch seam often except for when I stitch my backings together. If I am using 44" fabric to make a large backing, I usually just stitch the selvages together using about a 1.25-inch seam and then trim the part containing the actual selvage off using a scissors as it is easier to trim it that way instead of using a rotary cutter and trying to trim the edge straight before stitching it together. I never thought of using this attachment when doing that wide seam. That is a great Idea! It will make it easier as the amount of fabric being handled can pull the seam off.