Child Car Seat Basics 101: Anatomy of a Car Seat 2022 Guide

Child car seats are designed to perform optimally in daily rides and car crashes, all while prioritizing child's safety. However, did you ever wonder:

What are the parts that make the car seat function so well?

Today we will be looking at the full anatomy of a car seat while explaining the functions and essential components that make a child car seat expert in safety.


Car Seat Anatomy

The shell

should car seat be in middle or side

Every child's car seat includes a shell that offers the seat structure and shape. 

The shell of the infant insert is made from a hard plastic, usually dense polypropylene. On the shell of the seat, parents can often find basic information about the car seat.

The label on the shell will include installation instructions and rear-facing height and weight limits. In addition, parents can find valuable information on whether the infant car seat can be installed with a carrier. Unfortunately, not every infant car seat has this option, so it's necessary to check the label on the shell and the car seat manual.

Carrier handle

The carrier handle only exists on infant car seats. The handle allows for easier portability when switching vehicles or taking your car seat to the house or stroller.

The attached handle on the car seat has several positions. The manual instructions will inform you how to properly position the carry handle once the seat is installed in the vehicle.

Car seat base

Infant car seats will always include a car seat base. On some infant seats, the base is detachable, while some seats have an integrated car seat base.

However, infant seats are not the only ones with a car seat base. Usually, you will find the base is a part of an all-in-one or convertible car seat. In this case, a convertible car seat will have an integrated base that cannot be detached.

The car seat base can be installed with LATCH or a vehicle seat belt and offers a secure car seat fit. The carrier or the car seat is then firmly attached to the car seat base via a built-in locking mechanism. The base can remain installed in the vehicle, while the portable carrier can be removed for convenience.

Car seat bases like Britax offer a SafeCell technology that absorbs all the crash forces into the base.

Harness & buckles

  • Harness: Rear-facing infant car seats include a five-point harness with five attachment points covering a large area of the child's body. Every harness is made from tight webbing, which can endure thousands of pounds by restraining the body from forwarding motions in a crash.
    The five-point harness offers adequate support and restraints for the baby's shoulders, crotch, and chest area. In the middle of the harness, you can find a chest clip that should be positioned at the armpit level.
    The harness levels must be correctly below the child's shoulders for rear-facing rides. Check the manufacturer manual for the harness wash, as not all harnesses endure harsh soaps.
  • Buckle: The crotch buckle clips into the harness at the center. Depending on the design of the harness buckle, you can adjust the most secure and comforting position for your baby's fit.
  • Chest clip: The chest clip is designed to hold the harness straps buckled in. Thanks to the chest clip, the harness straps are always in the proper direction, even in the case of collision.
  • Harness pad covers: the harness pad covers are not a part of every infant car seat. A comfortable harness pad can be easily removed from most car seats.
  • Adjuster strap: The harness adjuster strap is on the bottom of the car seat, below the harness.
    The strap is activated via a button. Once you push the button up or down (depending on the mechanism), the harness webbing is loose. By pulling the harness strap forward, the harness is tightened for a secure fit once the baby is in the car seat.
    Do the pinch test to check the tightness of the harness once you are done. You should be able to slide only one finger under the harness if it's adequately tightened.

Shoulder belt guide

what are the parts of a car seat called

A shoulder belt guide is a part of high-back booster seats. Once the high-back booster seat is installed, the shoulder belt is guided through the shoulder belt guide for a secure fit.

In some high-back booster seats, the shoulder belt guide can be adjusted to achieve perfect wear by positioning it in a higher or lower position. The adjustable headrest on boosters will also allow for simultaneous shoulder belt guide adjustment.

Tether anchor

The top tether anchor is used for optimal stability and safety of forward-facing car seats. As a result, top tethers are rarely used with rear-facing seats.

Thanks to the top tether, forward-facing car seats are stabilized in the rear seat. Once a forward-facing car seat is secured with a tether, the seat prevents the child's head from forceful forward motions in the event of a collision.

A tether strap is made from webbing resembling a seat belt. One end of the tether strap is anchored to the car seat, while the other part attaches to the slots behind the back seat vehicle.

LATCH connectors (UAS)

The Universal Anchorage System (UAS), or LATCH, is a metal connector clip that attaches to the lower anchor connectors of the vehicle.

Almost every car seat allows you to install it using a LATCH or a vehicle seat belt. Always check the manufacturer manual before installing the car seat with either of the methods.

Infant insert & padding

Every car seat includes padding, usually made from plush materials. The seat padding provides comfort and safety by offering a protective layer between the baby's body and the car seat shell.

Infant inserts are a necessary part of rear-facing infant car seats. The infant inserts are designed to fit newborns in a snug fit. Once the baby has outgrown the newborn weight limit of the insert, you can remove the padding easily.

The head pad of the newborn insert is often detachable, so you can use it for longer if your baby needs extra head support.

Recline indicator

Infant car seats include a rear-facing recline indicator on the car seat base. Every car seat base is different, so the indicator can either be in the form of a line, bubble, or dial.

The car seat manual will inform newborns and babies about the proper recline angle. For example, newborns should ride at a 45-degree recline angle to prevent constricted airways.

Recline lever

A recline lever is also not a part of every car seat. Usually, a recline lever is found in rear-facing car seats. The lever is often located on the car seat base, but check the manufacturer manual to find this information. As the child grows, the car seat recline can be easily adjusted via a lever.


anatomy of a car seat

Armrests on the child's car seat accommodate the comfort of the occupant of the seat. High-back boosters usually have armrests that begin at the seat's shell and end above the pelvic area.

Most armrests are height adjustable, so they can be positioned appropriately to comfort the child.

What to Look for in a Car Seat?

Infant car seats

When purchasing infant car seats, check for the following accessories and features:

  • 5-point harness
  • A front harness adjuster to tighten the harness
  • A rain cover is optional but convenient for traveling
  • Make sure the car seat can recline up to 45 degrees
  • Carry handle makes portability much easier
  • Shock-absorbing foam in case of collision
  • Stroller compatibility

Convertible car seats

When buying convertible car seats, make sure these features are included:

  • Large weight limit (at least 50 lbs in rear-facing position)
  • Tether straps for safer installation
  • Non-returnable harnesses (preferably a 5-point harness)
  • Adjustable head rest

Booster seats

Booster seats are designed for older children weighing over 40 pounds. Consider the following features:

  • Check if it's compatible with the lap and shoulder belt in your vehicle
  • Ensure your kid is ready to ride in a booster (5-step car seat test)
  • Adjustable head support
  • Check if your vehicle has headrests. If the vehicle has headrests, you can opt for a backless booster.


What are the components of a car seat?

Car seat components are shell, base, car seat carrier, handle, padding, harness straps & buckles, UAS connectors, shoulder belt guide, and tether anchor.

What are child car seats made of, and why?

anatomy of convertible car seat

The hardware part of the child car seats, or the shell, is made of dense polypropylene plastic. The soft part of the seat padding is made from EPP foam, the best shock-absorbing material. The high-density sponge increases the comfort while also absorbing all of the crash energy.

The car seat's shell uses polypropylene as a heat-resisting material that offers safety and resistance. The high-heat resistance material will not be damaged under 150 degrees of external impact.

What makes car seats unsafe?

Car seats are unsafe under faulty installation. If the seat is not installed correctly, then the seat cannot function for optimal safety.

Car seats are also unsafe if used after expiration, damage, or crash. Be careful of purchasing second-hand car seats of unknown history as they are often dangerous for your child.

What kind of foam is in baby car seats?

Baby car seats' padding is made from EPP foam and EPS foam. The Expanded Polypropylene foam (EPP) and expanded Polystyrene foam (EPS) have exceptional insulation qualities while offering a lightweight design. In addition, the foam reduces vibrations while delivering stability in a car seat.

Final Words

Every child's car seat is different. However, we listed the essential parts every child's car seat features to ensure optimal safety.

We hope you learned more about the anatomy of a car seat and can now safely choose the best car seat option for your little more passing!

Avatar of Kathy Warner

Kathy Warner

Kathy is a busy mother of two and a CPS technician for more than eight years. Her mission is to awaken parents to the importance of child passenger safety and show them the right practice. You can read more about her here

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