Abstract: Employee #1 was riding on the back of a Hostler yard tractor, helping another driver secure the fifth wheel on the trailer. The trailer was too high for the pin to properly engage the fifth wheel on the truck. The truck backed under the trailer further than normal, pinning the employee between the cab and trailer. The driver stopped the truck and pulled forward as soon as he realized what happened. Employee #1 walked to the office and was then transported to the hospital, where he was examined and released. The employer did not enforce his own safety rules prohibiting riding on the rear of the yard tractor, and has been cited.