Sewing holes are pushed through the calf with a saddlers awl. If I also make a hole in my finger, the blood remains as a testament to my occasional flight of fancy.
Many leather workers succumb to puncture wounds every year
On the left, finished with saddle soap, dubbin, and a light coat of carnauba wax. On the right, a bloody (my saddlers awl is sharp) wallet ready to saddle-stitch.