A gate assembly for a trailer having a support deck (12), which provides for the gate assembly to be moved between a closed position in which both a lower gate member (30) and an upper gate member (32) are stacked and extend upwardly one upon the other and an extension position in which the lower gate (30) member extends forwardly from an end of the deck (12) as an extension of the deck and the upper gate member (32) extends upwardly from the end of the lower gate member (30).