Chart folios are the folder of charts used on board a ship in which charts are kept in a systematic manner. Folio covers are mode of canvass or other appropriate material capable of holding charts. A list of charts within it and a table of correction record is posted outside of the folio cover.
Chart folios are used to maintain the list of charts in numerical order for case of reference-
A ship playing all over the world and having no fixed route may maintain international folio system or standard folio system, maintained by the company as per BA number thus BA 1 to BA 300 may be listed in folio BA 301 to BA 600 may be listed in folio 2 & so on.
This a ship that is making voyages around Indian subcontinent may be having only one or two folios, plying area may be geographically divided in two zones & ship will then have two folios with one folio having eastern zone & ship will then have two folios with one folio having eastern zone charts & other folio having western zone charts.
The International convention for the safety of life at sea (Solas 1974) states; All ships shall carry adequate and up to date charts, sailing directions, list of lights, notices to mariners, tide tables and all other nautical publications necessary for the intended voyage (Chapter V, Reg 20).