The Instruction Manual is treasure that can be obtained in Sly Cooper: Age of Thieves in the episode In the Air Tonight. It is worth 287 coins and the time needed to reach the safehouse is forty seconds.
"Any self-respecting pilot worth his salt would absolutely cherish an instruction manual. It teaches the pilot how to fix their own planes, which is a marvelous thing to know how to do in a pinch. Why it continuously mentions monkey wrenches is a mystery, though."
It is located in the opposite hangar to the safehouse on the other side of the level. Sly needs the Repairman Costume to get this treasure.