A stonemason chips a 250-pound block of sandstone into a round and impressive projectile.
Lead is melted and poured into molds. When the metal cools, the weight is bolted to the trebuchet's shorter arm.
If the trebuchet works as planned, gravity will pull the six and a half tons of lead downward, the other arm will lift upward, seesaw-fashion. This will launch the sling-nestled ball with tremendous force at the castle wall and smash it.