When a WordPress update is interrupted, the site can get stuck showing a "Briefly unavailable for scheduled maintenance" message. Fixing it used to mean connecting over SFTP to delete a hidden file. Now you can clear it with one click.
Open a website, go to the Tools tab, and select Deactivate Maintenance Mode. The tool removes the file holding the site in maintenance mode and confirms once the site is reachable again.
See Stuck in maintenance mode for the full guide.