The purpose of this template is to have a single location for the Naval Vessel Register (NVR) ship detail base url as a method of combating link rot.   Usage  The template takes two parameters:  – (required) the ship's case-insensitive hull classification symbol in one of five forms: SSBN-659 – the preferred format because it matches the format for hull classification symbols generally used for US Navy ships throughout Wikipedia SSBN 659 SSBN659 SSBN_659 SSBN_659_1635 – the NVR file name format as of September 2017 There are exceptions.   has a unique hull classification symbol that must be used in this template exactly as shown.  There are three ships listed at the NVR website that do not have hull classification symbols.  These are: , , and .  For these three ships, use the ship's name for this parameter.  The code word OLDIRON, previously used to identify Constitution, is no longer supported.    – (optional) a title or label for an external link Parameter names are not required.  When not used, the positional order is: {{Naval Vessel Register URL|id|title}}  When  is empty or omitted, the template produces a url suitable for use in  and  templates. {{cite web |title=USS Zumwalt |website=Naval Vessel Register |url={{Naval Vessel Register URL|DDG-1000}} |accessdate=1 October 2016}}  With a title, the template produces a properly marked up external wikilink: {{Naval Vessel Register URL|DDG-1000|USS ''Zumwalt''}}  There are three ships listed at the NVR website that do not have hull classification symbols.  These are: , , and .  For these three ships, use the ship's name for this parameter.  The code word OLDIRON, previously used to identify Constitution, is no longer supported.  {{Naval Vessel Register URL|constitution|USS ''Constitution''}}  Error messages Module:Naval Vessel Register URL returns error messages when it cannot return a link into the NVR.  These error messages are: required parameter missing – displayed when  is empty or omitted from the template call; add a hull classification symbol malformed hull classification symbol:  – the value assigned to  is not one of the supported hull classification symbol forms; use a supported form unable to find group: [''] in Module:Naval Vessel Register URL/নথি nvr_ships_id – the data tables used by the template are grouped by hull type (the letter portion of a hull classification symbol).  This error message indicates that the hull type could not be found in the data table.  Check for a typo or, if a new hull type, add the hull type data to Module:NVR/নথি (further instructions there) unable to find hull classification symbol: [] in Module:Naval Vessel Register URL/নথি nvr_ships_id – the hull classification symbol value assigned to  was not found in the data tables; check for a typo in the number portion of the hull classification symbol or, if a new ship, add the ship data to Module:Naval Vessel Register URL/নথি (further instructions there) no identifier for hull classification symbol: [] in Module:Naval Vessel Register URL/data nvr_ships_id – the tables in Module:Naval Vessel Register URL/data have a listing for the ship but the listing is incomplete; add the missing data to Module:Naval Vessel Register URL/নথি (further instructions there)  Errors occurring on main-space pages are categorized at .  See also   ব্যবহার    আরও দেখুন