When Yu Lan traveled through time and became a guard in a border city of the Song Dynasty, the first thing he did was to be tied to the tower and wait to die - the Jin army's 100,000 iron cavalry came to the city, and the decaying city wall fell down as soon as it was pushed. Everyone was waiting for him to be trampled to a pulp. But the lost "Ten Thousand Jun Barrier" construction method from "Lu Ban Shu" suddenly appeared in his mind, which can recast a copper wall and iron wall in just half a day. That night, the commander of the Jin army was about to order a general attack, but he saw the entire ruined city wall rising from the ground overnight, and the 60-foot-tall composite arrow tower reached into the sky, and even the ladders used to climb the city could not be hung. Yu Lan stood at the top of the city and patted the dust: "Why are you panicking? This is just the first section. I plan to build the Great Wall to the entrance of the Jin Kingdom Palace - who among you can help me send a construction drawing?"
