Definition: Generate an appropriate title for the given text. The generated title must be short and include the main topic of the text. The preferred titles are under fifteen words.
Input: They appeared overnight between Tuesday and Wednesday. The only clue as to who carried out the work are tags from the "Bollard and Chicane Protection Authority". Yarn bombing, also known as guerrilla knitting, is a type of street art using items made from yarn - whether knitted, crocheted, or made into pom-poms.

'Yarn bombers' strike on Dumfries cycle path