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How can I sew a sausage dog draft / draught excluder? - sausage dog draught excluder pattern

I have some big project Cath Kidson dog sausage exclusion

http://www.retrotogo.com/2007/10/cath-kidston-do.html

and I was a doing. I found the snake pattern, which say they can be customized for a dog, but do not tell you how to sew on the head!

Can anyone help?

Thank you!