There’s one seaming situation that’s not covered by mattress stitch as we’ve talked about it so far (well, there are actually lots of situations that might not be covered by mattress stitch, but it’s a common finishing technique), and that’s when you need to work on a horizontal seam rather than a vertical one. So the shoulder of a sweater, say, instead of the side seam.
This stitch is known as faux Kitchener stitch, because it gives you an invisible seam that looks a bit like grafting. (You could also just call it an invisible horizontal seam.)
To make it, instead of going into the ladders between the stitches, you’re taking your sewing yarn behind the stitches on the edge of the knitting. Similar to mattress stitch you need to keep a handle on your tension here so the seam isn’t loose or puckery.
Have you ever worked this kind of seam? I’d love to hear any tips you might have!