Examples:

• The negotiations concerning the new Treaty take place too often behind closed doors.
• The candidate has been behind closed doors.
• Hey, you don't know what goes on behind closed doors.
• The process was conducted in a closed group, behind closed doors.
• Much of immense value is occurring behind closed doors.
• This has all taken place in secret, behind closed doors.
• The importing States were subject to decisions adopted behind closed doors.
• How can you say that this has happened behind closed doors?
• No-one knows what goes on behind closed doors.
• Just do it in your room, behind closed doors.