There are so many things to worry about these days when you're out in public. I hate to add one more thing to the list, but if it helps one person, then it's worth it.

There's a new trick out there for crooks to steal from you and it is apparently quite effective. It involves a simple plastic bottle.

If you ever see a plastic bottle (like an empty water bottle) stuck between your tire and the frame of your car, then you need to take action, like calling 911.

This trick was first reported in South Africa but has quickly spread to the rest of the world.

Here's how the trick works. When a potential carjacker sees a vehicle they want to steal, they stick a water bottle against the wheel to "mark" it. They put the bottle on the front passenger side wheel so the driver doesn't see it when entering.

When the car starts moving, the empty plastic bottle crackles making all kind of worrying noises. The first thing most drivers do at that point is to stop the car and get out to see what's the matter.

That's when the carjacker strikes!

If a driver leaves the keys in the car with the vehicle running, all the thief needs to do at that point is jump in and drive off. Or, some thieves are using that opportunity to get into the car and quickly steal valuables like wallets or cellphones left behind.

So, next time you're getting into your car, take a few seconds to check the wheels. If you see something like a water bottle jammed into the space between the tire and frame of the car, be on alert. A would-be thief may be watching you.

Quietly take out your phone and dial 911. Alert police as to what you are experiencing and provide your location and details about your vehicle.

It's crazy that we even have to write about stuff like this but we just want to help you to be aware and stay safe.

Below is a video explaining the scheme. It's in Spanish but you'll still get the gist of it.