Lex built it in his room and called me in.
"Look what I built, Daddy!"
"Oh that looks good. What is it?"
"It's a light switch form."
"A light switch form?"
Then Lex goes over near his door and starts using the construction to try to turn the light on and off. The handle kept coming off, but once he got the idea to ignore the handle and hold it from one end, it worked marginally better.
He's since built the Light Switch Form 1.5, which is longer and stronger, but still has problems because his fine motor skills are a bit rough. But, being his parents, we were pretty impressed.
Of course someone called Lex is meant to build evil inventions, but hey, he has to start somewhere.