How does the Fido puzzle work?

The "Fido puzzle" is not a well-known puzzle. It's likely you're thinking of a different puzzle, or perhaps a specific scenario involving a dog named Fido.

To help me understand what you're asking, could you please provide:

* More context: What kind of puzzle are you thinking of? Is it a logic puzzle, a word puzzle, a physical puzzle?

* Any additional details: What are the rules of the puzzle? What is the goal? What is the specific scenario involving Fido?

Once you provide more information, I can help you understand how the puzzle works!