What's a good answer?

As we rambled through the World War II section of the Air Force Museum, my niece pointed at a plane. "Daddy! Daddy! What is that?"
My brother folded down to preschooler eye level. "You mean the metal above the wheel?"
"No! That!"
"Do you mean the wheel?"
"No! That!" She stabbed her finger out again, waving in the vicinity of the wheel.
"That's a chock, honey. That's to keep the airplane from rolling away."
She stomped a foot, face screwed up in a scowl. "That's stupid! They should use ropes, like you do!"

...

"See this? These long ones running the length of the wing are spars. And these ones running front to back are ribs."
"Airplanes have ribs? Are they ticklish, too?"