“Secret Passages,” she whispered.

“Eh?” Taffy said. “What’s that?”

Jennifer T. got up and, carrying the handbook, began searching the walls of the cell for what the book described as Telltale Signs of a Secret Passage. “Look for a section of the wall,” the anonymous author had written, “or, as it may be, of the ceiling, which is of a different shade or hue, however slightly, than the rest.”

and

The next recommended technique was, of course, tapping. Jennifer T. knelt down at the bottom of the wall by the door and began to tap, working her way up and down, using the spine of the handbook itself, listening for that Telltale Hallowness.

It’s wonderful when fictions include facts, real or imagined. See The Fantastic Mr. Fox (film), when Mr. Fox, outlines the master plan to Kylie he tells him “Beagles love Blueberries”.

Or Chuck Dugan is AWOL. A novel stocked full of Naval “facts”. I suspect most are real.

These “facts” make the worlds they inhabit vivid.

Chabon, Michael. Summerland: A Novel. New York: Hyperion Books for Children, 2002. (pp 294-295)