What a fabulous idea! Works for airplane tickets and passports and similar items, too…

So, you’re going to a ticketed event, like a concert or a ball game. It’s out of town. You’re carpooling with four other people. How do you ensure that everyone in the car has their ticket with them?

The car doesn’t move until each person takes out their ticket and holds it to their forehead.

(quoted from 43 Folders: The Forehead Ticket Trick)