Ezek 4:2-3

2and put siegeworks against it, and build a siege wall against it, and cast up a ramp against it; set camps also against it, and plant battering rams against it all around.3Then take an iron plate and place it as an iron wall between you and the city; set your face toward it, and let it be in a state of siege, and press the siege against it. This is a sign for the house of Israel.