Saws and planers commonly used in carpentry are said to have been invented by Lu Ban. Once, Luban wanted to build a palace. He and his disciples took axes and went to Nanshan to cut wood. Cutting down a tree with an axe is tiring and slow. It has been blowing for more than ten days in a row, and the cut wood is far from the need. The day of construction is approaching, and Lu Ban is very anxious. One day, he went to a steep mountain top to look for wood. He was struggling to live and climb, when suddenly his finger was cut by thatch and his blood flowed. Lu Ban thought, why is thatch so powerful? He forgot the pain in the wound and concentrated on studying thatch. He found that there were dense and sharp teeth on the edge of the thatch. He scratched his hand with those fine teeth, and sure enough, it was another cut. This made Lu Ban jump for joy, he thought. Imitate the appearance of thatch and make iron bars with fine teeth on the edges. He used this iron bar to pull the tree, which was really fast and labor-saving. It took only a few days to prepare the wood. This kind of iron bar with fine teeth is the ancestor of the saw we still use today.