A few days ago I finished a patch knife for black powder shooting. A knife without a sheath isn't a knife. So I got some leather, a needle, and some artificial sinew from Leatherhead, read this webpage, and got down to it.
I can't claim any real innovation. I used Gorilla glue to attach the welt to the side of the sheath instead of Duco or some other contact cement. It worked well.
I don't have one of those cool tools that mark the stitch holes and my leather was too thin to gouge a stitch channel. I filed a rounded conic on the end of a steel rod. I used this to emboss a channel in the leather 1/8" from the edge of the welt. I decided quite arbitrarily that the stitch holes should be 3/16" apart and fashioned a suitable spacer. I worked my way down the embossed channel using my spacer, a very pointy awl, and some authority to leave a hole every 3/16". Don't do this on your dining room table without a backing board.
As per the instructions, I used a two-needle system to lace the sheath together then shaped the sheath using acetone.
I decided to waterproof the sheath by dipping it in paraffin wax. You can find Gulf brand wax in the canning section of the grocery. I melted 8 ounces of the wax using a low-rent double boiler made by floating a sufficiently sized microwave-save disposable food container in a pot of boiling water. It took about 15 minutes to melt 8 ounces of wax. Easy pease. When the wax was melted I just dropped the sheath in the container and rolled it around to get even coverage. Then I fished it out with a wire, let the wax drain, and set it aside to cool. I did this twice. When I was done I snapped the lid on the container and let it cool. The wax is ready for storage until next time.
The wax bath turned the sheath nearly black. It looks nice but was surprising to see it happen. Unfortunately the wax scratches very easily showing the natural leather underneath. Next time perhaps I'll stain the sheath first. In any event I can dip it again when the opportunity presents itself.
Here's a barrage of pictures.