Final answer:
The slow moving vehicle sign on a truck is placed on the rear of the vehicle to indicate that it is moving at a slow speed.
Step-by-step explanation:
The slow moving vehicle sign on a truck is usually placed on the rear of the vehicle. It is typically a reflective, triangular sign with a red border and a bright orange center. This sign is used to indicate that the truck is moving at a slow speed, and other drivers should exercise caution when approaching or passing the truck.