(1.2 to 3.1 in) wide and 1.5 to 2 millimetres (0.059 to 0.079 in) thick. They are put together in three layers, so that the total thickness of the wood layer is 4.5 to 6 millimetres (0.18 to 0.24 in). It was likely well made and extremely sturdy. Advantages and disadvantages The scutum was light enough to be held in one hand and its large height and width covered the entire wielder, making him very unlikely to be hit by missile fire and in hand-to-hand combat. The metal boss, or umbo, in the centre of the scutum also made it an auxiliary punching weapon. Its composite construction meant that early versions of the scutum could fail from a heavy cutting or piercing blow, which was experienced in the Roman campaigns against Carthage and Dacia where the falcata and falx could easily penetrate and rip through it. The effects of these weapons prompted design changes that made the scutum more resilient such as thicker planks and metal edges. The aspis, which it replaced, provided less protective coverage than the scutum but was much more durable. Combat uses According to Polybius, the scutum gave Roman soldiers an edge over their Carthaginian enemies during the Punic Wars: "Their arms also give the men both protection and confidence, which they owed to the size of the shield." The Roman writer Suetonius recorded anecdotes of the heroic centurion Cassius Scaeva and legionary Gaius Acilius who fought under Caesar in the Battle of Dyrrachium and the battle of Massilia, respectively: The Roman writer Cassius Dio in his Roman History described Roman against Roman in the Battle of Philippi: "For a long time there was pushing of shield against shield and thrusting with the sword, as they were at first cautiously looking for a chance to wound others without being wounded themselves." The shape of the scutum allowed packed formations of legionaries to overlap their shields to provide an effective barrier against projectiles. The most novel (and specialised, for it afforded negligible protection against other attacks) use was the testudo (Latin for "tortoise"), which added legionaries holding shields from above to protect against descending projectiles (such as arrows, spears, or objects thrown by defenders on walls). Dio gives an account of a testudo put to good use by Marc Antony's men while on campaign in Armenia: However, the testudo was not invincible, as Dio also gives an