All seatbelt systems are designed to lock in a crash. A correctly installed car seat should not move more than one inch (2.5cm) side to side and front to back *at the belt path*. A car seat needs to be what's called "pre-crash locked" at all times when it's in the vehicle so that it is correctly positioned prior to a crash.
To put it simply - the more your car seat is "one with the car" the less it will move in an accident meaning the occupant of the seat is less likely to hit the interior of the vehicle.
Because the webbing in a seatbelt will by nature "stretch" (nylon usually stretches up to 13% and polyester 7% - which is used now in virtually all vehicles) the more rigidly your car seat is installed in to the vehicle again, as above, the less it will move in an accident.
Knowing the features and capabilities of your seatbelt system will help you to correctly install your car seat. Please remember that this information is written for those living in New Zealand - therefore some of it may not apply to other countries with different vehicles or child restraint systems.
Terms to know:
Retractors: Gather and store extra webbing in the vehicle. Most lap/shoulder seat belts have one retractor at the shoulder. Some do have one at the shoulder and one at the floor (however this is not very common).
Anchors: This is the place where seat belts or tethers are attached, generally at the factory, to a strong location.
Buckles: Buckles are commonly referred to as the "female" part of the seatbelt. They "accept" the latchplate and hold the seat belt in place.
Latchplates: Are commonly referred to as the "male" end of the seatbelt. Latchplates are the seat belt part that connects the seat belt webbing to a buckle in the vehicle.
Webbing: Webbing is the fabric part of the seatbelt that crosses the person or holds the car seat.
Locking clip: A locking clip is a device which clamps the tightened cars lap and shoulder belt together at the latchplate to make the lap belt a fixed length.
Lock off: A lock off is much like a locking clip. Lock offs are devices provided by the car seat manufacturer built into the car seat that acts just like a locking clip, clamping the tightened vehicle seat belt together.
A seatbelt with a switchable retractor fits an adult comfortably and will lock only in an emergency such as a sudden stop, crash or turn unless switched to the locking position. This position switches to a tight, pre-crash locked seat belt to install a car seat.
To switch the retractor to "locking" mode, gently pull webbing all the way out of the retractor (until you can pull no more out).
To install a car seat when the retractor is in "locking mode" route the belt through the correct seat belt path and buckle. Put the retractor into locking mode (see above), apply weight on the seat, tighten the seat belt, feed the extra webbing back onto the retractor then check for a tight installation.
Most seatbelts that have a switchable retractor have a label sewn in to the bottom instructing how to use the retractor to lock in a child seat. It may also be in Japanese, so not always in English.
An Emergency Locking Retractor (ELR for short) looks like a switchable retractor but does not have the ability to switch to "locking mode". An ELR locks only in a sudden stop, turn, or crash. When the webbing of the belt is pulled all the way out, it still moves in and out freely.
An Emergency Locking Retractor can not be used to install a car seat without another locking feature (such as a locking clip) or a latchplate that locks (read below re: latchplates).
Seat belts with emergency locking retractors can be found in lap-only, shoulder-only, or lap-shoulder belts.
To test to see if the belt you are using has an Emergency Locking Retractor:
Pull all of the webbing out of the retractor
Allow some of the webbing to go back into the casing
Try to pull the webbing out again very slowly
If the webbing goes freely in and out of the casing, you might have an emergency locking retractor
It would be quite a rare occurance for you to come across a vehicle that is equipped with ALR belts, however on the chance that you do - it would be helpful to know how to use this system.
An Automatic Locking Retractor can be found on a lap only belt or a lap/shoulder belt. Automatic Locking Retractors (ALR for short) are generally easy to use in regards to car seat installation. Once the seat belt is passed through the car sea tbelt path and buckled, the seat belt can only get shorter (and hold the car seat tighter) once pressue is applied on to the car seat.
To test to see if the belt you are using has an Automatic Locking Retractor:
Pull the webbing out slowly and gently (so that about 46-50cmof webbing is exposed)
Once you stop pulling the webbing to see if the retractor locks, allow a small amount of webbing (about 8-16cm) to go back into the retractor. Then, gently pull on the webbing. If no webbing comes out, then the retractor is an ALR type.
Some seatbelts with ALR may apear to have no locking ability if they are tested when they seatbelt is extended just a very short distance (less than 30 to 46cm) from the retractor casing. That 30 to 46cm space is known as the "dead zone". Therefore, the retractor might not "activate" till the webbing is pulledd out 46cm (18 inches) or more.
Free-sliding latchplates are found only on lap/shoulder seatbelts. A sliding latchplate has no locking feature and no moving parts. A free sliding latchplate allows the belt to slip easily between the lap and shoulder portions.
To test to see if the latchplate you are using is free-sliding:
Buckle the seat belt and pull up on the lap portion of the seat belt.
The seat belt should not lengthen if the latchplate has a pre-crash locking feature.
This type of latchplate on a seat belt is usually found on "lap" belts in the centre rear of some vehicles. This type of seatbelt is generally good for car seat installation.
This latchplate has a locking bar found on the bottom or back (as pictured).
If the seat belt and latchplate lie flat and in alignment then the latchplate will lock. However, if the latchplate is on an "angle" and the latchplate and seat belt webbing are perpendicular then it will not lock.
To check to see if the latchplate locks:
Buckle the seat belt.
Give a firm tug on the lap portion of the seatbelt while pulling up on it (making the seat belt and latchplate parallel).
The seat belt should not slide through the latchplate under a moderate tug, if it doesn't - then it is likely that you have a locking latchplate
Sewn on latch plates are found on lap and lap/shoulder seatbelts. These types of latchplates are relatively "rare" to come across in New Zealand vehicles however it is still helpful to know about them because they do exist. A sewn on latchplate has no locking feature and no moving parts.
Some vehicles (though again, you might not come across a vehicle in New Zealand with this feature) have a switchable latchplate that uses a button to move from the adult pre-crash position to the child pre-crash locking position. An adult may need to adjust the button. This keeps children from playing with the button. Look on the back of every latchplate to see if a button is available.
Not all pre-crash locking latchplates look the same. Some have a bar (as pictured), others have a sliding or rotating metal or plastic piece. The locking piece clamps down on the lap part of the seat belt when buckled. When pulled slightly up and forward, much as if a body were moving in a sudden stop, it locks.
To test to see if you have a Light-weight Locking Latchplate:
Buckle the seat belt
Give a firm tug on the lap portion of the seat belt while pulling up on it (makes the seat belt and latchplte parallel).
Remember that the seat belt should not slide through the latchplate with a moderate tug.
Different styles of locking clips
A locking clip or lock off device is . Please remember this list is by no means all inclusive, there are bound to be more styles of locking clips or lock off devices that are not listed below. To make things easier I've used "LC" as an abbreviation for "locking clip".
This tends to be the most common type of locking clip used. It is also often referred to as an "H clip". These locking clips are usually gold in colour though they can also be silver in colour.
To use it you must:
Thread the seatbelt through the correct belt path for your car seat
Tighten it by applying weight in to the seat and pulling up on the shoulder belt (feeding the excess webbing in to the retractor).
Grip the webbing just above the latchplate together with your fingers, unbuckle the seatbelt (making sure not to let go of the gripped webbing or letting it slide).
With your hands then fit the "H" locking clip within an inch of the latch plate in such a way that you can see all of its "bars" facing upwards, visible to you - rather then facing away from you. Safety wise it doesn't really matter if they are facing you or not, however this is one sure way to know whether you have the locking clip fastened correctly.
Again apply weight in to the seat whilst simultaneously buckling in the seatbelt again
Check the car seat for movement *at the belt path*. There should not be more than one inch (2.5cm) of movement at the belt path side to side or front to back.
This "red" locking clip comes with some seats sold in New Zealand. Whilst you can, if you'd prefer to, use another style of locking clip, the manufacturer of some certain types of seats (the Nania Nuevo for one) provides this one themselves to assumably make things easier for you. The "red" locking clip is usually attached to the seat by means of a small length of string.
To use it you must:
Thread the seatbelt through the correct belt path for your car seat
Tighten it by applying weight in to the seat and pulling up on the shoulder belt (feeding the excess webbing in to the retractor).
Grip the webbing just above the latchplate together with your fingers, unbuckle the seatbelt (making sure not to let go of the gripped webbing or letting it slide).
With your other hand, open up the red locking clip, position it within an inch of the latch plate then close the clip firmly (making sure that it is securely fastened).
Again apply weight in to the seat whilst simultaneously buckling in the seatbelt again
Check the car seat for movement *at the belt path*. There should not be more than one inch (2.5cm) of movement at the belt path side to side or front to back.
The exactus locking clip is pretty straight forward and uncomplicated.
To use it you must:
Thread the seatbelt through the correct belt path for your car seat
Tighten it by applying weight in to the seat and pulling up on the shoulder belt (feeding the excess webbing in to the retractor).
Grip the webbing just above the latchplate together with your fingers, unbuckle the seatbelt (making sure not to let go of the gripped webbing or letting it slide).
With your other hand, open up the exactus locking clip, position it within an inch of the latch plate then close the clip firmly (making sure that it is securely fastened).
Again apply weight in to the seat whilst simultaneously buckling in the seatbelt again
Check the car seat for movement *at the belt path*. There should not be more than one inch (2.5cm) of movement at the belt path side to side or front to back.
The exactus locking clip may not be a suitable option for all car seat installations, therefore it is important to find the locking clip most appropriate for you.
Safe-n-Sound (Britax) have their own style of locking clip. While it's function is the same as any other locking clip - it does look quite different. There can be some difficulty in fitting this style off locking clip as it can be somewhat time consuming, therefore you might perhaps find another style of locking clip easier to use.
To use it you must:
Thread the seatbelt through the correct belt path for your car seat
Tighten it by applying weight in to the seat and pulling up on the shoulder belt (feeding the excess webbing in to the retractor).
Grip the webbing just above the latchplate together with your fingers, unbuckle the seatbelt (making sure not to let go of the gripped webbing or letting it slide).
With your hands then fit the 3 Bar Gated Buckle within an inch of the latch plate in such a way that you can see all of its "bars" facing upwards, visible to you - rather then facing away from you.
Again apply weight in to the seat whilst simultaneously buckling in the seatbelt again
Check the car seat for movement *at the belt path*. There should not be more than one inch (2.5cm) of movement at the belt path side to side or front to back.
Please note that sometimes this style of locking clip must be placed on the "opposite" side. I.E. Instead of within an inch of the latchplate, it needs to be placed closer to the door. This is only for child safety harnesses when a lap/shoulder belt needs to be converted to a lap belt.
A Belt Shortening Clip looks much like a normal "H" locking clip. It's usually silver in colour and usually taller/bigger than a normal locking clip. However - you can not ever tell whether or not it is a Belt Shortening Clip just by looking at it. Belt Shortening Clips are made of special alloys that means that they are stronger then generic locking clips.
You can use a belt shortening clip as a normal locking clip for normal purposes. However, you can not ever use a normal locking clip as a belt shortening clip - they are not strong enough and can increase the risk of injury.
Belt shortening clips are generally used with seat belts with ELR (emergency locking retractors) and sewn on latch plates. They are also used with types of seatbelts found in some front seats of older cars with motorized shoulder belts and a seperate lap belt. There are also some "people movers" that have ELR lap belts with sewn on latch plates that require a BSC to securely install a car seat.
Use a belt shortening clip as a last resort. Try and see if there are any other alternatives before you use one as using one can increase the risk of injury if used incorrectly.
Belt shortening clips are not sold in New Zealand however if you do need one - I do have my own stock of belt shortening clips - please contact me for more information.
A belt shortening clip takes the place of a retractor, as all the webbing is pulled out of the casing and shortened with the belt-shortening clip. It firmly ties off and locks fully extended seat belt webbing to provide a fixed lap belt length.
How to use a BSC:
Fit the lap belt (on an ELR) through the correct belt path and buckle it in.
Apply weight in to the seat whilst gathering and pinching off all the extra webbing on the retractor side so that it does not move more than an inch side to side and front to back.
Once the excess webbing has been pinched off with your fingers unbuckle the seat belt (making sure not to let the webbing slip) fit the belt shortening clip.
To fit the belt shortening clip you fit it much like a normal locking clip, except that the extra loop of webbing your left with "doubles back" through the prongs (making the loop visible). Doubling back ensures the clip will hold the webbing tight even in a crash.
See the below pictures that demonstrate how to use a belt shortening clip.
Installing a belt shortneing clip is not something you should ever attempt alone this information here is strictly for informational purposes only.
Not many technicians have experience with belt shortening clips so it is important that you find a Child Passenger Safety Technician and enquire as to whether or not they have experience in their use. Belt shortening clips are not taught in the Safe2Go curriculum therefore you will not find a Safe2Go Technician that knows how to use them.
These types of lock offs are found on the Graco Logico S sold in New Zealand. They are incredibly easy and straight forward to use.
To use the lock off:
Open the lock off, leave it open whilst threading the seatbelt through the correct belt path and buckle in the seat.
Tighten the installation by applying weight on to the seat and if using a lap/shoulder belt, pull on the shoulder portion simultaneously (feeding the excess webbing back in to the retractor).
Close the lock off
Check the car seat for movement *at the belt path*. There should not be more than one inch (2.5cm) of movement at the belt path side to side or front to back.
This style of lock off is found on Safe-n-Sound (Britax) car seats. They are usually present on their "higher end" models of seats (such as the Royale, Meridian AHR and Platinum AHR). For seats of lower models that do not have these forward-facing lock offs you can purchase them from the manufacturer (Britax Childcare Ltd.) or your local Plunket Car Seat Rental Scheme and fit them yourself.
These lock offs are used on lap/shoulder seatbelts. You can not use them on lap belts. If you do not get a satisfactory installation with this lock off, you can use a locking clip.
You must only use one forward-facing lock off at a time (the one closest to the retractor). It is not possible (nor safe) to use both at the same time.
To use the lock off:
Thread the seatbelt through the correct belt path and buckle in the seat.
Tighten the installation by applying weight on to the seat and pull on the shoulder portion simultaneously (feeding the excess webbing back in to the retractor).
Open the lock off by pressing its lever
Fit the shoulder portion of the belt through
Firmly close the lock off by pushing it
Check the car seat for movement *at the belt path*. There should not be more than one inch (2.5cm) of movement at the belt path side to side or front to back.
This style of lock off is found on the Safe-n-Sound Platinum AHR car seat which is a "higher end" model of Safe-n-Sound car seats.
These lock offs are used on lap/shoulder seatbelts. You can not use them on lap belts. If you do not get a satisfactory installation with this lock off, you can use a locking clip.
You must only use one rear-facing lock off at a time (usually the one closest to the retractor/door side). Generally you do not use the lock off on the buckle side because the latchplate/buckle can interfere with the lock off and damage it.
To use the lock off:
Make sure that the lock off on the "door/retractor" side is open, make sure the buckle side one is closed.
Thread the seatbelt through the correct belt path and buckle in the seat.
Tighten the installation by applying weight on to the seat and pull on the shoulder portion simultaneously (feeding the excess webbing back in to the retractor).
Firmly close the lock off by pushing the "arm" across and closing it
Check the car seat for movement *at the belt path*. There should not be more than one inch (2.5cm) of movement at the belt path side to side or front to back.
Sometimes the lock off is difficult (if not near impossible) to close therefore you may have to use a locking clip.
National Child Passenger Safety Certification Training Program - Student Manual - April 2007 (much of the information found on this page is in reference to information found in this manual)
All seatbelt systems are designed to lock in a crash. A correctly installed car seat should not move more than one inch (2.5cm) side to side and front to back *at the belt path*. A car seat needs to be what's called "pre-crash locked" at all times when it's in the vehicle so that it is correctly positioned prior to a crash. 
