It was literally an “armoured” vehicle used in sieges for the leveling of ground and the backfilling of defensive ditches for the easier approach of other siege machines. It consisted of a wooden cage on wheels and a hipped roof covering approximately 120 square metres for the protection of the digging and ditch-filling crew. Its exposed walls, like all the other war machines, were covered with iron sheets, fresh wickerwork, clay mixed with hair, and padded rawhide and lambskins (stuffed with vinegar-soaked straw or green seaweed) in order to neutralise incendiary arrows and to absorb the blow of stones launched by the enemy. An ingenious placement system of the axle wheel bearing allowed its forward, sideway and diagonal movement. On another tortoise, the digging tortoise, the front face was vertical to enable better contact with the wall and easier sabotage by the diggers.