Flickering lines on screen

Hi teagirl,

Thanks for participating in the Apple Support Communities. From your post it appears that you see the menu bar on the top and bottom of your screen, and there are lines on one side. If you haven't done so already, restart your Mac. Sometimes simply restarting can fix unexpected behavior. If you continue to notice the issue, test by creating a new administrator account with these steps: Set up users, guests, and groups on Mac. If you see it in the new account, it would be best to get your Mac evaluated at an Apple Store or Apple Authorized Service Provider.

You can also reach out to Apple Support directly. They can be contacted here: Get Support, or by calling the most applicable phone number from this list: Contact Apple for support and service.

Best regards.