Chevrolet Low Cab Forward 4500 2019 Series Owner's Manual page 60

Storage 59
Cargo loading caution Incorrect Correct
Do not place cargo only at the front or only at the rear. Distribute it
evenly.
When using supports under cargo, position them uniformly along the
cargo.
To the greatest extent possible, do not allow long cargo to protrude
beyond the rear edge of the cargo bed. Rather, use supports to raise it
at an angle. Avoid supporting it using just the front guard frame and the
rear edge of the cargo bed.