The incident unfolded at 4.15pm when a 76-year-old woman opened her door to a man who said that he could carry out repair work to her roof.
The woman told him that no such work was required and promptly shut the door. Her next move was to contact police who want to use this incident as an example.
They fear that there are vulnerable residents in Cumbernauld and Kilsyth who could be conned by an individual who has no qualms about taking advantage of vulnerable people.
A spokesman said: “Politely decline their offer and close the door. We have the same advice about cold callers on the phone. Never give personal information to someone you don’t know.”
Anyone else who has encountered this man is asked to contact police on 101.