There are many things in life that we seem to accept without questioning them. Since certain things have always been a certain way, it never occurs to us to ask “why.” Well, that is, until you have kids who want to know why the sky is blue, and then you find yourself very, very thankful for the internet and search engines.

One of those every day things that you probably have never thought too much about is the escalator. You’ve probably seen them in stores, malls, office buildings, etc. Escalators are so common, and they all look pretty similar.

There’s the hand rail that never seems to move at quite the exact same speed as the stairs. There’s the metal stairs which move at the perfect not-too-fast, not-too-slow speed. There’s the metal part on the floor where you have to carefully step onto the escalator, and there’s the top of the escalator which you have to watch for so you step off at just the right time.

Once again, unless you’re a child seeing these moving stairs for the very first time, you probably don’t question what they look like or how they work, but if you want to impress your family or your office, here’s a fun fact you might find interesting. It turns out that the stairs on escalators are designed to serve a function that you probably didn’t know about. 

Picture escalator stairs. They are gray. They are metal. They have grooves in them. We can’t think of any other type of staircase that is made up of grooves.

We always assumed the groves had something to do with the movement of the escalator, and while that is partially true, that is not the entire reason.

At the very top of the escalator where the top step flattens out and you have to step off, there is a ridge that’s called a comb plate. This comb plate cleans the stairs by sweeping the grooves and eliminating any debris that may have fallen on the stairs. Cleaning the stairs is a way of sure, keeping them clean, but also preventing any large object from entering the escalator mechanism and thus preventing the escalator from jamming and temporarily breaking down.

Now you know what a comb plate is and why escalator stairs have grooves. That’s your daily dose of trivia.