Police are appealing for information after nine cars were damaged in Abbots Langley.
The offences occurred between 7.30pm and 8.30pm on June 21, when a person or people walked along The Greenway and scratched the vehicles.
PC Dani Howlett-Bolton, who is investigating, said: "Thousands of pounds of damage has been caused to these vehicles in broad daylight and I would appeal to anyone who saw anything suspicious in the area or who knows who is responsible to contact me with information.
"I would be particularly keen to hear from anyone who may have seen a group of youths in the street that evening."
Anyone with information is asked to contact PC Howlett-Bolton via the Herts Police non-emergency number 101 quoting crime reference number C2/14/1274. Alternatively call Crimestoppers, the independent charity, anonymously on 0800 555 111.