Childhood memories of illegal egg selling

My background is working class, my father worked in a glass factory and his employment was considered essential, otherwise he would have enlisted in the Royal Navy. My mother cleaned houses to earn extra money.

My fascinating story regards the delivery of eggs to our house during the war. A local chicken farmer presumably was selling extra eggs illegally and only when it was dark, his method of communicating with his customers was to use his fingernails against the glass in the door to announce his arrival. I assume that would have allowed my parents to indicate that it was safe for him to continue with the sale and that other members of the public weren't on the property to report his illegal activity.