When you finish a project and have parts left over:
https://www.bbc.com/news/world-us-canada-50409531
A 10-week-old abandoned puppy with a secondary tail, in the middle of his head, has been taken in by an animal rescue centre in Missouri.
Staff at Mac's Mission, which is predominantly for animals with special needs, have called the puppy Narwhal.
They had been told there was "no medical need to remove" the extra tail as it caused him no pain, they said.
And the popularity of photos of Narwhal on Facebook had helped raise awareness of the rescue centre's work.