Two employees were trying to retrieve a piece of glass that was buried at the back of a rolling A-frame cart. One of them was holding up pieces of glass (each about 60 by 80 inches) that were leaning out from the stack. Their weight, pushing against the base of the cart, caused the wheels to move. The glass then fell onto the employee, pinning him against the horizontal bar of a piece of equipment about 5 feet away. He suffered internal injuries.