An employee loaded a single stick of 6-inch pipes onto this trailer. There was dunnage under the front end of the pipe. The employee asked a co-worker to assist him by lifting up the end of the pipe so he could place dunnage under the back end. When the back of the pipe was lifted, the pipe shifted and started to fall off the trailer, catching the employee's arm between the pipe and the trailer. The employee suffered a broken elbow.