Possible Clues:

• Its lines have lines
• Teleprompter alternative
• Stick in the snooker hall from one of those in a suit - the commentator sees it and reads it as it is
• Line holdup?
• Stage holdup?
• *Actor's prompt
• Emcee's visual aid
• What a TV host often reads from
• This might help TV presenter, wanting line articulated with wit
• It helps prevent stumbling