Simple kashaka half-shell (customizable)

Given that there aren't too many snuffbox trees growing in Canada, I had to improvise when trying [kashaka](https://en.wikipedia.org/wiki/Kashaka)s. You're probably better off buying the real thing.

Pick the diameter to suit your hand size in Customizer. Smaller might be better. Make sure that the central hole is just big enough to let the string pass through, but not allow the stop knot to pass through. The standard wall thickness may be too heavy, but should print on most machines.