the ultrasonic module is only a PCB with four pins, and we need to fix it on the car. the ultrasonic module should be placed vertically, however, there is not a vertical surface of the body of the car.
I made a vertical surface at the bottom of the car, and fix the HC-SR04 on it with cable ties and tapes. So now the ultrasonic module become a "car backing radar" :)
the ultrasonic module is only a PCB with four pins, and we need to fix it on the car. the ultrasonic module should be placed vertically, however, there is not a vertical surface of the body of the car.