I'm not a prolific maker of sheaths, but I use the hand stitching and piercing method that Al Stohlman describes in "The Art of Hand Sewing Leather". Yes, there are very well illustrated design plans in the back of the book for a stitching pony . . . and the pony looks to be very versatile and practical. I just never had the time to start another project in order to make one for myself.
I used the low cost Tandy pony for years. Up until about a year ago, they only offered one very simple and almost rudimentary pony. I bought one years ago and have cursed it almost since day one. I could rant for a while about the downfalls, but won't. Now they have a nicer one that looks much better. This raised my interest and made me consider an upgrade.
After looking closely at the new Tandy pony and doing some comparisons, I bought a pony last week from someone in Wisconsin off of Ebay for well under $100. The pony measures a total of 16.5" tall. The clamps are 4" wide and the base is 16 3/4" by 5" 3/8.
The wood clamp loosens and tightens with a large wing-nut on the side that requires little effort to hold and release your project. The clamp (base) also swivels 360 degrees for added convenience. The hinge at the base of the clamp is spring loaded so it automatically closes on your project to hold it as you tighten the wing-nut.
I received it today, and found the claims to be accurate and true. I can't wait to use it this weekend. I have no affiliation with the Ebay seller.
Since I work on small projects like sheathes, I may end up modifying it to reduce the "depth" of the clamping jaws as indicated by the blue mark-ups in the image below. So far though, I've prevented myself from becoming involved in another project and feel that I bought a nice pony at a reasonable price.
Just a suggested alternative to making your own.
