We'd recommend archiving. This way they will not be visible on the board anymore however you can still refer back to them via the "Archived Items" section in the board.
You can also archive all cards in a list by clicking (...) in your "Done" list and select "Archive all cards in this list".
More information about archiving is available here: http://help.trello.com/article/795-archiving-and-deleting-cards
As a Jira power user, I was at first doubtful that Trello could benefit my workflow. Jira already uses boards (ones you can customize!), so why would I even need to use Trello?! In this post you will...
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