Described by Polybius, Livy, Silius Italicus and Plutarch, this spectacular machine hooked onto the bows of Roman ships approaching the walls of Syracuse to lift them out of the water. The mechanism consists in a base with supports, on which is a beam left free to oscillate and act as a lever. The counterweight at the end performs a "snap" function, to make it more effective once the bow has been captured. When suddenly released, the vessels overturned in the sea.