Have you had your child’s car seat inspected by a certified child passenger safety technician? If you haven’t, it’s definitely worth a trip to your local inspection station (typically your local firehouse) to see how you did.

According to the National Highway Transportation Safety Administration (NHTSA), about 73 percent of car seats have at least one “critical” misuse. I wrote about five of the most common car-seat mistakes parents make with car-seat installation, according to a National Highway Transportation Safety Administration (NHTSA) study, in a recent post for Productopia.com. In the study, NHSTA researchers pinpointed the seat errors by surveying 4,167 drivers who came to certified child passenger safety inspection stations in 24 randomly selected geographic areas in the U.S.

With most of the errors, the car seat was too loose—either the harness or the seat itself. Another boo-boo, one I didn’t include in the piece: Not using the top tether to secure the car seat. “Many parents are confused by the top tether strap that comes with all convertible car seats. They aren’t sure what to do with it and will sometimes just tuck it away in the back of the seat,” says Allana Pinkerton, a child passenger safety advocate for the car seat manufacturer, Diono. Sound familiar? The top tether strap is important because it helps secure the top of the car seat to the car, to reduce how far a child’s head will go forward in an accident. Car seats are tested with the top tether is use. Some though, such as Diono’s Radian RXT, exceed federal safety standards even without the top tether, Pinkerton says. Don’t risk it though. Use the top tether as directed by your car seat’s instruction manual.

In general, crash forces can be so strong and unpredictable that if the seat isn’t a snug fit and secured properly, kids can get propelled forward or out of the seat, risking injury or death.

Car seats are complicated. So do your homework. Before attempting to install your child’s car seat, read your car seat’s manual, read your vehicle’s instruction manual and watch the installation video on the car seat manufacturer’s Website if it’s available. Finally, make sure your work passes inspection. To find a car seat inspection station in your area, visit www.safercar.gov.