A tow bar assembly has a shank portion for attachment to the towing vehicle hitch, a pivot joint on a trailing end of the shank, and two arms extending from the pivot joint for attachment to the towed load. A stowage block on the shank includes two transversely oriented slots, for receiving a tab on the arms and thereby hold the arms in a transverse, horizontal stowage position. The arms each telescope between extended and retracted positions. A latch, having a retention shaft with a handle, automatically engages to lock the arm in the extended position when the trailing end of the arm is pulled to the extended position. The retention shaft has a shape which, depending on its rotational position as controlled by the handle, either allows the telescoping or interferes with the telescoping, locking the arm in the extended position.