How to understand "black and white generals guarding the door"

According to legend, a long time ago, Nanping area often suffered from heavy rains and floods, coupled with the tyrannical donation of court officials, and the people's lives were very poor. Unbearable, they organized to boycott taxes and donations, and the team grew stronger and stronger. After receiving the report, the court sent two brothers, General White and General Black, to lead the troops to suppress it. White-faced generals are handsome and white, while black-faced generals are as black as charcoal. These two brothers are not only brave, but also kind, honest and frank. When they came to Nanping to know the truth, they felt sympathy. Not only did it not suppress the people, but it also led everyone to fight against the boundary. They started talking, dredging rivers, building dikes and dams to eliminate wind disasters and floods. This angered the imperial court and sent a large number of officers and men to crusade, and the wind, magic and water gods also cheered. In an instant, the wind roared, the waves rolled, the sky was dark, and the sun and the moon were dull. However, the two generals were fearless and bravely resisted, repelling the repeated attacks of court officers and soldiers. By noon the next day, I was tired and hungry In the end, because they were outnumbered, they were losing ground.

The white-faced general's hat was swept away by the strong wind, drifted to the north and landed on the other side of the river, becoming the present Bamboo Hat Mountain. After the saddle fell down the front hill, it became the present Maanshan. The whip fell to Sanxiang, Zhongshan City, and became a land called whipple. The horse, who was good at fighting, fell to the ground and died. People call this place a racecourse. The black-faced general's hat was blown to the west by the strong wind and turned into a bun mountain. The horse leg was cut off and rolled down the Hongwan River, which became the present horse leg village. Two horse eyes were dug out by the enemy and thrown to the west, turning into two big stones, which became the present Shuangshi Village.

Unwilling to be humiliated, the two generals stood side by side in the wind and resolutely turned into two mountains. These two mountains are the same as their skin color, one is white and the other is black, so people call them General Mountain with White Face and General Mountain with Black Face. The enchanter tried his best to blow the two mountains down, only blowing a hole at the junction of the two mountains, which was called Fengmen 'ao. ? In order not to forget the kindness of the two generals, people burned incense and sacrificed on a mushroom stone at the foot of the mountain.

Over time, everyone called this big stone incense burner stone. The descendants of the two generals also specially built a mountain road, which is now Aoshizai Road. They knelt in front of their father and wept bitterly for three days and nights, and their grief could be heard from miles away. People call this place Dapuyi. The crying tears flowed into a canal and gathered in a barren place, which people called Zibai Hall. Because these two mountains stand tall, they block the wind and waves at sea and protect the people from the wind disaster. Since then, Nanping people have been farming and fishing, living and working in peace and contentment.