Cross-jack – The lower yard on the mizzen or aftermost mast of a ship-rigged sailing vessel to spread the sheets of the mizzen topsail. It was so called because the term mizzen yard was in use for the lateen sail which was later replaced by the trapezoidal spanker sail set under a gaff. From about 1800 some ships set a square sail called the cross-jack from the cross-jack yard but it had limited use because of the interference with the spanker.