It's not much to look at, but this odd shaped little piece of leather is one of the most useful things I own.
...it is the guard I wear on my finger whilst Clicking.
'Clicking' is shoemaker-speak for cutting-out-leather-pieces-using-a-really-sharp-knife.
On the left there is my clicking knife. I've had it since 1999 and it started off with a longer, hooked blade, but years of sharpening has left it short and straight, but still effective.
This is how I hold my clicking knife.
I extend my index finger so that the tip of my finger is next to the tip of my knife. This way the knife feels more like an extension of my body, and I am always aware of exactly where the pointy end is!
There can be a lot of pressure on the index finger as the hand pushes down on the knife and draws it through the leather. I wear the leather guard to stop the blade digging into my finger. Without it, there's the chance that the blade can damage the nerves and tendons of the finger.
Such a handy little piece of kit!