Experts say four-out-of-five car seats in the U.S. are not properly installed.

East Tennessee Children's Hospital's injury coordinator says the numbers they see locally are even higher than that.

"If we see 20 seats at a check point, usually 19 or 20 of them are wrong," said Alexis Keiser-Yawn.

Keiser-Yawn said most parents make two critical mistakes: lockability and harnessing.

Many parents will tighten their child's car seat with a seat belt or the latch system, but Keiser-Yarn said that doesn't lock the car seat into place.

"You think the car seat is in right and installed correctly, but in the case of an accident it's not locked, so it's going to fly with the child," said Keiser-Yawn.

When it comes to harnessing, she said it's all about the positioning of the chest clip. Keiser-Yawn said it should be at the sternum bone even though many kids prefer to push it down. 

"The problem is without that chest clip, it's not holding that child in the harness. So in the case of an accident they are going to come out of the harness," she said.

There are hundreds of car seat models out there to choose from. Keiser-Yawn said the one that's right for you and your child has a lot to do with what vehicle you drive. 

Convertible car seats keep getting bigger to accommodate higher weight limits, so Keiser-Yawm said the size of your car should play a big factor in choosing a seat.

She recommends everyone take their seat to an expert who can make sure it's installed correctly. 

"We have over 60 partners in a 20-county surrounding area, mostly police and fire departments, and you can call, make an appointment and go get the car seat checked," said Keiser-Yawn.

For more information about those car seat check points, you can visit East Tennessee Children's Hospital's website