We knew that our son was destined to be an engineer when, not long after his first birthday, he used a plastic toy screwdriver to take the bottom pin out of the front-door hinges. Evidently he wanted to go out to play, and wasn’t happy about being locked inside with a double-sided deadbolt. We nabbed him before he could put together a scaffold to climb up and reach the upper pins (he understood that concept very well, too).