You need a piece of strong leather (about 2mm), wide enough to wrap around the thumb at the base and a little bit longer than the thumb is from tip to base.
[url=http://www.fletchers-corner.de/cpg/albums/userpics/10321/daumenringa.jpg]
![Bild](http://www.fletchers-corner.de/cpg/albums/userpics/10321/thumb_daumenringa.jpg)
Put your thumb on the rough side of the leather and draw the contour. add a few millimetres on all sides, remember you can cut off leather later, but you can't make it grow again.
[url=http://www.fletchers-corner.de/cpg/albums/userpics/10321/Daumenringb.jpg]
![Bild](http://www.fletchers-corner.de/cpg/albums/userpics/10321/thumb_Daumenringb.jpg)
You can see the dimensions quite well in the following picture. By the way, my hands are not very large, so if you are a blacksmith by profession, start by making the pattern at least one square wider and longer (squares are 5mm).
Use a punch to make the holes (about 3mm diameter).
![Bild](http://www.fletchers-corner.de/cpg/albums/userpics/10321/daumenringc.jpg)
The elongated sleeves which will be on the top of the thumb are tapered for two reasons: a larger contact area with the skin keeps the thumbring from slipping ; and it fits better, because the curve follows the rounded thumb joint. Otherwise the sleeves would stick out as soon as you bend the thumb. I also use the elongated sleeves to fasten a a safety sling, which goes around the wrist, to the thumbring.
Should prevent loss.
[url=http://www.fletchers-corner.de/cpg/albums/userpics/10321/daumenringd.jpg]
![Bild](http://www.fletchers-corner.de/cpg/albums/userpics/10321/thumb_daumenringd.jpg)
[url=http://www.fletchers-corner.de/cpg/albums/userpics/10321/daumenringe.jpg]
![Bild](http://www.fletchers-corner.de/cpg/albums/userpics/10321/thumb_daumenringe.jpg)
So that's what it looks like when finished. Don't let the sleeves overlap - this creates a stiff ridge that is uncomfortable. It is also a better idea not to use leather lacing like the one shown in the pictures. Use flat lacing, or, even better, shoestrings. Not "authentic", but soft.
At first the ring will seem awfully stiff, but that will change soon when you start using it. Use oil or fat to increase flexibility, make it resistant against humidity and sweat and make the leather lose that brand-new colour.
Once you started using it, tune the thumbring by shortening and narrowing the lip that protects the tip of the thumb as much as possible.
I also scrape the cutout for the base of the thumb to thin it. If it is as thick as the rest, you will always fell it press into the base of the thumb, even if the cutout is very large. But then the fit might become too loose.
I have no idea how long it will take until a thumbring like that is worn out, but as making it costs you 10-15 minutes of time and just a small piece of scrap leather and a piece of string, there should be no problem in making one every few months!
Happy thumbing, or whatever you say... !