These pens are so much easier to see with my tired old eyes than chalk. It also gives a more precise mark and doesn't spread like chalk sometimes does which can cause me to make a mistake and sew a seam a few millimeters off. I have a lot of sewing experience but rarely make anything anymore because fabric, thread, buttons, etc., are all more expensive than buying a ready made item. One exception I do make is robes. I prefer thin, non stretchy cotton robes that are oversized and reach the floor. And, I like to use cute fabric and pretty trims such as sparkly sequins and ribbons. This being said, I mark a lot with this pen to line up seams, patch pocket placements and trim placement. These pens arrived just as I was becoming motivated to make some robes. I purchased fabric a few years ago specifically for robes. I made a robe for me and one for my adult daughter before I burned out. Fortunately, now I'm motivated again and I'm also teaching my daughter to sew so we each get a pen to make our own robes.Aside from marking patch pocket placement, all of the marks I made are hidden and actually vanish by the time I finish off the seams. However, this ink will wash out the first time I wash the robe or, I can spot wash it but I don't because it usually leaves a water spot after it is dry.