I see a lot of these in old buildings about 3 feet of the ground, but have still to work out what they are for. UPDATE via a friend on Facebook “Milk doors were usually adjacent to the kitchen or pantry, approximately 18 [inches] by 18 [inches,] located at waist height, and lined with metal,” Carl Handman, an architect with ECH&H in Pennsylvania, tells Urbo. “There were two doors, one on the outside, trimmed and painted to match the exterior, and one on the inside, rimmed and stained or painted to match the interior of the kitchen. They were used by your milkman to deposit your daily supply of fresh milk, cream, and butter.”
