How to Use a 5-Point Car Seat Harness

Toddler in rear-facing car seat
2014, NHTSA Photo Library.

A five-point harness is the webbing portion of the car seat that adjusts over the baby to hold him in the seat. The five points in the name are the spots where the harness webbing attaches to the car seat. Two of the points are at each shoulder, two of the points are at baby's hips, and the final point is where the harness buckles between the baby's legs. Most car seats in the U.S. have a five-point harness.

How to Adjust the Height of the Shoulder Straps

On almost every car seat, there are ways to adjust the height of the shoulder straps. On some seats, you need to rethread the straps to move them to higher or lower slots. On other seats, you move a head rest up or down and the shoulder straps move up or down with it; this is called a no-rethread harness.

While no-rethread harnesses can make it easier to adjust the height of the shoulder straps, they can also make it harder to tighten the harness straps as there is often more friction in the system. On rear-facing car seats, it is easy to rethread the straps as baby grows and doesn't require uninstalling the car seat. A no-rethread harness is more important on a forward-facing car seat as it saves you from having to uninstall the car seat to move the straps up as your child grows.

Proper adjustment of the harness is key to car seat safety. The shoulder straps must be at or below the child's shoulders when rear-facing, and at or above the child's shoulders when forward-facing.

Tighten the Harness

The harness should be tightened so that you can't pinch any excess harness webbing. Never skip this very important step; you need to do it every time you buckle your baby in.

  • Slide chest clip down to baby's belly. Leave it here while you tighten the straps.
  • Position yourself at the head of the car seat and pull up at the shoulder straps to remove slack.
  • Most car seats have a tail of webbing that comes out of the seat between baby's feet. The next step is to get straps snug by pulling firmly on that webbing tail.
  • If your car seat doesn't have a tail like this, check the user's manual to see how to tighten the harness. There may be a buckle on the back of the seat or knobs on the side.
  • Move chest clip up to armpit level after the straps are properly snug.

How to Adjust the Crotch Buckle and Hip Straps

The crotch buckle (the attachment point between baby's legs) may be adjustable, and if so, it should be placed according to manufacturer instructions, usually as close to the child as possible.

Some car seats have an adjustable hip width on the harness. Just like selecting the slot for harness height, you can also select a slot to bring the harness in closer to the baby's hips, and then move it out again as the baby grows.

How to Untwist Straps

The harness should be smoothed before each use so it isn't tangled or twisted. When you put the child into the car seat and then take them out again, it's easy for the harness straps to become twisted as they move under and around baby's body.

Not smoothing the straps out can quickly lead to straps that no longer lay flat and are instead wound tightly like ropes. Twisted straps are dangerous as they concentrate crash forces over a smaller area of the child's body compared to straps that are straight and laying flat. There are two ways straps can become twisted, and two ways to fix them.

How to Buckle Your Child in a 5-Point Harness

It usually helps to have the harness straps loose when putting baby in. Make sure baby is sitting all the way back in the seat and is not slouching. Then, like putting on a vest, put baby's arm through the harness straps.

When done correctly, the straps will go over baby's shoulders, down the chest and belly and over the hips, and buckle between the legs. After both tongues are clicked into the crotch buckle and the chest clip is closed, it is time to tighten the harness.

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