This is useful when you don't necessarily want to remove the board button completely, but instead wish to restrict usage temporarily. Rather than having users select the job board button when jobs may not be published anyway, it may be beneficial to restrict usage until the issue is resolved.
You'll now see a "locked" badge displayed next to the Board Name in the Board list.
You will also see the locked board in your Account Summary.
The button cannot be selected and users that have access to that board will see a lock icon on the job board button.
When hovering over the "Details" users will see the note that was entered in step 3.
To remove the lock, simply go back into the board instance edit page, deselect the "Lock" checkbox and 'Save changes'.
Make sure you've resolved the job board issue, otherwise users may post to a board that is not processing the jobs.