Batteries Not Included

Here's a prop that could be used for all kinds of key learning points.
Batteries.

I was reading about an analogy with batteries and can see how to use them the following way.

Take a pair of batteries and insert them wrong way in to a small device, like a flashlight. Nothing happens, no power. Then read the little positive and negative signs and put them in the right way. Suddenly power.

How I Would Use This

It is important to take the time to set things up properly. Great tools (like batteries) can become useless if we don't take the time to figure out how to use them.

A simple device, but I think a good one.