A big part of learning to use knitting sheath is learning to properly secure it to your body. Different knitting sheath designs work best with different kinds of cowbands .I have made different designe of knitting sheaths and tested them with different kinds of cowbands.
A few representative knitting sheath designs.
(the ruler in the center is 6" long)
Thus, when you are making a knitting sheath, you need to think about what you are going to wear as you knit, and how you are going to secure the knitting sheath.
My first success with knitting sheaths came after I saw the Hornblower series on PBS. I saw the sailors (costumed as British navy circa 1800) wearing heavy leather belts, very low on their hips. I realized that a knitting sheath could be tucked in to such a belt (over the right buttock) for gansey knitting. This worked so well that I used heavy leather belts for all my knitting sheaths for a long, long time. For knitting very firm fabrics with long needles, nothing surpasses a heavy leather belt.
Knitting sheaths that work well with heavy leather belts.
However, not everybody wants to knit with long gansey needles, some want to knit with shorter needles. The heavy leather belts are not the best solution for using a Yorkshire goose wing knitting sheath with sock needles, or for using larger needles for producing softer fabrics.
Shorter needles and the production of softer fabrics allow the use of other kinds of cowbands. One that works remarkably well is the elastic waistband of sweat pants (or gym shorts in the summer.) Some kinds of knitting sheaths do well tucked into an elastic waist band.
I like wearing an apron when I knit. In the winter, it is a bit warmer. In the summer, a good apron helps protect my lap from the sharp tips of very fine needles. And, a white apron can reflect a lot of light onto dark yarn, and a dark apron can reduce glare when knitting outside. Apron strings are one the very best ways to secure a knitting sheath. A lot of my knitting sheaths are now made to work with apron strings.
Some knitting sheaths designed to work with apron strings.
As I knit, there is some downward pressure on the working needle as I knit, but I put a lot of effort into learning to knit so that I do NOT pull the needle out of the needle adapter or the knitting sheath out of my cowband. However, most knitters do tend to pull up on the needle. The slot in the knitting sheath for the cowband must have edges to resist both up and down forces.
The knitting sheath on the right above does not, and thus while it works well for me with apron strings, it would not work well for most knitters. Most knitters would want to use that knitting sheath only with a heavy leather belt .
I had some success with thin synthetic belts as in:
These require narrow slots for the fabric and the knitting sheaths must be held on the belt in some way, or most knitters will pull them up and off of the belt. This was a light weight knitting sheath for camping and the clew to hold the yarn went through the hole and held the knitting sheath on the belt.
Here is another approach that works for thin woven belts:
This is another photograph of one of the knitting sheaths on the blue apron above. That groove allows it to work well with a thin nylon belt. This photo also shows the narrow leather belt from my knitting pouch. The truth of the the matter is that narrow leather belt on the knitting pouch has become one of my favorite cowbands for knitting sheaths when knitting softer fabrics.
Knitting sheaths with strap from knitting pouch.
I also like (card) woven or knit sashes to hold a knitting sheath:
This is a garter stitch, knit sash that I wrap around my waist and tie, which works very with knitting sheaths when knitting softer fabrics.
If you only wear dresses and disdain belts, sashes, and aprons, then I suggest a knitting heart that is stitched to the dress. The stuff above is knitting gear that I know works very well, because it has been used and used. However, a nice dress belt, fresh from Needless Markup Department Stores will work just as well, and be more attractive. Likewise, I tend to use the prototype knitting sheaths that are functional, but not pretty.