I encounter an incomprehensible saying:
Except as a man handled an axe*, he had no way of knowing a fool.
while reading this tutorial.
*I wanted to add a mark here which means the possible error derives from the source
This is a quote from Spenser:
"Men of the wood and lumberjacks,
they judged me by the appropriate tool.
Except as a fellow handled an axe
they had no way of knowing a fool."
I take it to mean that people can judge you only in terms of things that they understand.
The speaker is saying that lumberjacks had no way to judge a man's importance or value or capabilities except by observing how he handled an axe.