I encountered a Shogi saying:
And I'm pretty confused about the ぬ there. If it was る I'd expect the meaning to be something like:
"If you have 3 knights, you can't be mated"
Well, while typing this I suddenly realized I can just search google for ぬ instead of る, so I'll guess I'll be answering my own question as I was encouraged to do on other StackExchange sites.