Hans Karrer Travel Wrench Impact Kerambit - im TATORT

What is a travel wrench?

The travel wrench is a revolutionary training tool and instructional system that compliments while improving tactical efficiency with any Tactical implement Proficiency in skill is cultivated through repetition and refining conceptual principles of instinctual response

A wrench is blunt, so your only going to be able to swing for the head to do any sort of real damage, meanwhile you've already been cut on your arms stomach and chest several times.
You'd be better off with a knife, a sword would be better but again not too heavy.