Related Clues:

• "Not another word!"
• 'Keep it down'
• "Keep it down!"
• 'Shut your trap!'
• “Hush!”
• Usher's admonition
• 'This is a library!'
• ''Not another peep!''
• Library admonition
• ''Not another word!''
• Finger-on-lips sound
• 'Keep it down!'
• "Shh!" (and a hint to the feature shared by the answers to starred clues)
• "Shh!" from a plumber?
• "Shh!" from a mail carrier?