Using Car Seat Lock Offs

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Secure Seat Belt InstallationsClose up of a lock off in a convertible car seat

  • What: Car Seat Lock Off hints
  • When: Birth to 80 lbs
  • Why: Secure car seats with seat belt installation
  • Where: Your vehicle

Since I bought my first car seat back with my eldest child, car seats have added an additional feature to help install their seats securely: lock offs. These clips go over (or in some cases the seat belt tucks under) the seat belt to take up the slack and keep the seat from moving more than an inch along the belt path.

Britax Roundabout convertible car seat shell without foam or padding showing lock off locations
Red lock offs for forward-facing installation and blue lock offs for rear-facing installation on a convertible car seat

Our Britax convertible car seats come with four lock off mechanisms installed in each seat, two along the back for forward-facing installation, and two along the bottom of the seat for rear-facing installation. Depending on the brand of your seat, you might not need both lock offs to install it properly. Read the owner’s manual to find out for sure. Manufacturers install two lock offs (even if you only need to use one) to make sure the lock off ends up on the correct side of the seat in relation to the seat belt. Having a lock off on both sides means you can install the car seat on both sides of the car, and it won’t matter which side the shoulder belt comes across.

But even if you only need one (why don’t they put LATCH anchors in the third row of vehicles? It’s not like it’s roomy enough for adults to ride back there.) lock off, it can be difficult to get the clip kind closed once you put the seat belt underneath.

Lock off peeking out from under the convertible car seat padding
A blue lock off for rear-facing installation peeking out from under the convertible car seat padding


The first thing to know is where to locate them. Once you find them buried underneath the foam and upholstery on the plastic shell of a convertible seat, then you need to get them open. That part is usually a cinch. But there are two parts to the lock off, one arm that opens in each direction. You lift up both arms before laying the seat belt across the divot created once both arms open. Click the seat belt into place, and pull it as tightly as you can, preferably with your weight on the seat to get it extra tight.

Close up of a convertible car seat lock off open
An open convertible car seat lock off

Now for the real trick. After you fold both arms of the lock off back down (they won’t lay flat, and the angle may prevent the second upper arm from coming down much at all), use your palm with your weight on it to get it to snap closed. Once you do, the seat belt should not budge. Using lock offs simplifies installation. Instead of pulling the seat belt all the way out and holding onto it with your teeth while pushing on a car seat to prevent the retractor lock from engaging until you’re ready for it to tighten, you lean on your palm on the lock off.

I recommend searching for images featuring your particular brand and model of car seat, to make sure you can locate and use the lock offs correctly. They make car seat installations so much simpler if you know where to look and how to use them.

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