Talk:Murakumo/@comment-25096087-20150331052031/@comment-24978536-20150331111118

Ship lock was a mechanism prerent in the Summer 2014 and Fall 2014 event, that prevented people from using the same ships in different operations. Events usually include multiple different maps, which are divided into operations: For example, Summer event had the AL Operation (maps E-1 and E-2), MI Operation (E-3, E-4, E-5) and lastly the counter attack of AL/MI (E-6). The ship lock works in a way that upon using a ship girl in an event map, her card is tagged with that operation she participicated in, and she will be unable to join different operations.

Here is the tag from Summer event AL operation for reference (the tag is removed after the event ends). The ships tagged with this tag were able to participicate in Summer E-1 and E-2, but not in the maps after that:

The ship lock forces people to prepare a large fleet with many high level ships of each type. However, even without ship lock it is in general preferable to have multiple high level ships of each ship type. You never really know what you will be facing and what kind of branching rules there will be after all. Combined Fleet is also a recurring thing, further making it preferable to have a large fleet for events.