Gap is the name of the ancient canal, located in Xingyang City, Henan Province. When Chu and Han contended, the dividing line was the boundary. Later, it also refers to the boundary of the territory.

"Historical Records of Xiang Yu": "Agreed with Korea to divide the world. The west is Han and the east is Chu. "

Shen Ming Cai's "Thousand Daughters": "Chu and Han are not in harmony, and the gap painting world is swallowed up."

Qing Xu Qin Cheng's poem "Baigou River": "Liang Ping holds the temple, who will cut the gap?"

Northern Zhou Yuxin's "Quasi-Forever" No.8: "Nagano hangs his wings at the beginning and turns in a gap." Ni Kun's Note: "Yuan Di has only been enthroned for three years. Wei Jun went to Xiangyang, and Damon Liang led the discussion, all of which were defeated. When Liang and Wei were divided into north and south, there was a gap. The imperial clan of the Liang Dynasty helped Wei cut himself, so the cloud turned against him. "