On city street corners, around telephone posts, through barbed wire fences, and over abandoned cars, a quiet revolution is brewing. "Knit graffiti" is an international guerrilla movement that started underground and is now embraced by crochet and knitting artists of all ages, nationalities, and genders. Its practitioners create works of art out of yarn, then "donate" them to public spaces as part of a covert plan for world yarn domination. This is...