I think you can work some sliding windows in there, eg.
"... and can only be told through a sliding window".
When you finish the joke, you could sit down for a ReST before retrying, upon which time an ICPM missile hurtles through the room at top volume, shattering everyone's ear drums. The colonel stands up from his teletype desk and hands you an explanatory note proclaiming either administrative prohibition on communications of this nature, and a news update that the local port is presently unreachable due to flooding, and that people should find their own alternate routes should they have business there.
"... and can only be told through a sliding window".
When you finish the joke, you could sit down for a ReST before retrying, upon which time an ICPM missile hurtles through the room at top volume, shattering everyone's ear drums. The colonel stands up from his teletype desk and hands you an explanatory note proclaiming either administrative prohibition on communications of this nature, and a news update that the local port is presently unreachable due to flooding, and that people should find their own alternate routes should they have business there.