ratlines

thumb|right|200px|Climbing the ratlines of STS Mir|STS Mir thumb|right|200px|Rat-boards and rigging of Christian Radich

Ratlines () are lengths of thin line tied between the shrouds of a sailing ship to form a ladder. Found on all square-rigged ships, whose crews must go aloft to stow the square sails, they also appear on larger fore-and-aft rigged vessels to aid in repairs aloft or conduct a lookout from above.