Whenever a load extends to the rear 4 feet or more beyond the bed or body of a vehicle at night the end and sides of the load must be marked by what?

Whenever a load extends 4 feet or more beyond the bed or body of a vehicle at night, the end of the load must be marked with a red light visible from at least 500 feet away. Additionally, the sides of the load should be marked with reflective devices or flags to enhance visibility and ensure safety. These markings help alert other drivers to the extended load and prevent accidents.