When I first started knitting dog sweaters, 20+ years ago, I wanted to be able to leash through the sweater to my dog's harness, which I keep on them all the time. All my dogs wear collars, but they only serve the purpose of holding tags. I don't like the idea of pulling on a dog's neck, especially ones with sensitive protruding eyes, like my Pekingese. So I made a buttonhole in the mid back of the sweater. For Madeline, she wears a longer harness (intended for being used in the car, but it's the only one I've found so far that fits), so the harness hole is a little further down her back.
I now see harness holes on lots of dog garments. I swear, people looked at Lucky Penny Hand Made and used my idea. Over the years I've wasted money on search engine optimization. I purchased key words on two different occasions for hundreds of dollars each. One was a search engine called Leapfish which never took off like Google or Bing. I've never gotten any hits from it. The other service would call every month to say that the word I had purchased for a few hundred dollars was now a few thousand dollars. Scam, anyone? I remember crying when I was talking with the sales rep to set it up. I was a little emotional about neediing Lucky Penny to be a success. A few years later, and Lucky Penny is still languishing. The only real success that Lucky Penny has had is Doggie Knits. That's the gift that keeps on giving. I'm still receiving royalty payments. It's published in three languages. I'm still working on growing it. Including taking some courses in launching a craft based business, and trying to stick my toe back in with a book publisher.