Probably shouldn't admit this for two reasons: there has already been enough blood and this lesson learned is far too serious, but here it is anyway. Never put a knife down on the bench without it's sheath and a corollary (that's something that follows logically from the first part), never cut leather in front of a customer! I was trying to be a nice guy, the customer was a pain. He wanted his holster his way, i.e. his pattern. And he wanted me to do the initial cutting where he could see it