Hi – yes the welt seems mysterious at first, but it is quite simple to add to any sheath and you should really not go without it. The welt is the only thing protecting the stitching from the blade of the knife. If you would like a better idea for how to size a welt you should take a look at my in depth tutorial on making a Leather Axe Sheath here. You may need to scroll through it a bit to get to the welt part. The key is to make sure it is wide enough so it is easy to stitch. Good luck!