The Spanker sail is on the rearmost mast, and in Drakes day was a triangular sail set diagonally across the Mizzen mast Lateen yard is the technical term. (back most mast on the ship) on later vessels it was set as a square sail on one or two booms stuck out behind the mast(Like a schooners sail) Fore and aft rigged,The action of the sail and booms helped steady the ship. The brailing rope was used to pull in the sail and spill the wind, then the sail was lashed up and stowed away in port...Hope this was of some help. Yours,Aye Dave