Ezekiel 4:2

and lay siege against it, and build a fort against it, very likely a watch-tower or bulwark, which permitted the invading army to observe every movement of the besieged, and cast a mount against it, the usual earthworks with their trenches; set the camp also against it, to surround the city on all sides, and set battering-rams against it round about, the latter being logs of hard wood, with heads of wrought iron. All this was to be shown in the sketch prepared by the prophet, the map thus emphasizing the fact that Jerusalem would be besieged.