"Two tigers guarding the door" is a metaphor that means two tigers guarding the door, making mules, horses and other animals afraid to go out, which in turn leads to them staying at home, increasing the chance of breeding. This statement comes from the dot distribution characteristics of Yuan Xiang’s chest and back edge. Counting from Yuan Xiang’s chest, there is a dot every four teeth. From right to left from the edge of Yuan Xiang’s back, there are also dots every two teeth. A dot, these two dots are like two little tigers guarding the statue of Yuan in the middle.