A buddy of mine had a ferrett trained to run to a bell. He would attach a fishing line to a harness and go to the other side of the crawl and open the nearest vent. Worked great for years until he got to a house w/ a cat w/ a bell on its coller. If you have ever seen what a ferret can do to a cat, I won't go further. He paid $500 for that freaking cat. Its funny now.
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