I just assumed if you have a twig and berries you were born with that knowledge. The fact a guy can be a 'contractor' and not know this about saws I would be very skeptical of what 'he' does 'know' and his work. But when I was a manager at autozone plenty of guys didn't know where to put fluids in car. Oil in radiator, coolant in washer fluid reservoir and a couple outer I seen happen in the parking lot guys making 6 figure salaries had 0 clue on there cars when needing something like is it a v6 or v8 sir? I'm not sure? I had to make plenty of trips outside to see what he had because a guy didn't even know what he is driving???