Is "Tunnel" the Heinlein book in which the "kids" are going off on their survival test, & get marooned? One of kids takes his older sister's advice (and her knife, as a spare) to carry a good blade, rather than some battery powered gizmo.

IIRC, you're right--excellent lessons in many of Heinlein's works, including "Farnam's Freehold" and "Friday", too.

I keep Fletcher's "Complete Walker III" near to bedside; it's about worn out...time to get another copy.

David