Trello does not offer any specific passcode that you can set on a per board basis. You (or the relevant board admins) are however in full control of access to a board.
For example, if a board is set to private only the members that are added by the board admin can view and edit that board. More on board visibility options in Trello is available here: https://help.trello.com/article/789-changing-the-visibility-of-a-board-to-public-private-or-team
Hello Community! My name is Brittany Joiner and I am a Trello enthusiast and Atlassian Community Leader. I'll be sharing with you a series of videos with my top tips on how to best use Trello...
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