As novice shipwrights, the Romans built copies that were heavier than the Carthaginian vessels, and so slower and less manoeuvrable. Getting the oarsmen to row as a unit, let alone to execute more complex battle manoeuvres, required long and arduous training. At least half of the oarsmen would need to have had some experience if the ship was to be handled effectively. As a result, the Romans were initially at a disadvantage against the more experienced Carthaginians. To counter this, the Romans introduced the "corvus", a bridge wide and long, with a heavy spike on the underside, which was designed to pierce and anchor into an enemy ship's deck. This allowed Roman legionaries acting as marines to board enemy ships and capture them, rather than employing the previously traditional tactic of ramming.