I was looking for the entry point point of the mains water pipe and was excavating on the exterior of the front brick wall by digging right beside the foundation, and 8 courses of brick below ground level I reached the footing of the foundation. I noticed that in one place on the first course of bricks above the footing, there was a missing brick creating an opening through the foundation. It seemed very deliberate. Any ideas what it could have been for? See the attached pic.