What is one requirement for the trailer when checking the kingpin?

The requirement for the trailer regarding the kingpin is that it must lay flat on the fifth wheel skid plate. This indicates that the trailer is properly connected to the fifth wheel of the truck, ensuring a secure coupling. When the kingpin is correctly seated, it allows for safe and stable towing, which is essential for maintaining control during driving.

If the kingpin is not properly seated or if the trailer is not laying flat, it could lead to issues such as swaying, detachment while in motion, or uneven weight distribution, all of which can compromise safety on the road. This ensures the structural integrity of the connection between the truck and the trailer, which is critical for safe transport.