​When you buy or use an ISOFIX child car seat, it will have the two ISOFIX bars on the back of the seat, and almost all ISOFIX seats will then have a third point of anchorage. This third point of anchorage is very important, as it prevents the ISOFIX child seat from moving too much in a collision. The third point of anchorage will either be a support leg, which is a very popular option, or a top tether. This article is focusing on the top tether – how to use it, what it does and the benefits.

What is a top tether?

The top tether is the third point of anchorage on an ISOFIX child car seat. It is a length of webbing which is attached to the back of the child seat, with a hook on the end. The top tether strap must have a green indicator on it to show when it has been pulled tightly enough.

How do you use a top tether?

​The top tether will pass over the top of the vehicle seat, and hook onto the top tether point. The top tether point will either be in the boot, on the back of the vehicle seat, or it may be in the roof of the car.

Top tether points are normally indicated with the anchor logo, or your car handbook will tell you where your point is.

What does it do?

As we have already mentioned, ISOFIX seats tend to have a third point of anchorage, which reduces dangerous movement of the seat in a collision. The top tether hooks behind the child seat onto the bracket in the car holding it in place, along with the ISOFIX arms.

In a collision, a child seat will move forward, and the seat can pivot on the ISOFIX arms. To prevent this from happening, and to also absorb energy from a collision, the top tether point is able to then reduce movement in the seat along with the ISOFIX, and absorb crash forces.

It is very important to ensure the top tether is used, if it is supplied.

What are the benefits?

Many ISOFIX seats have the support leg which reaches into the floor well, and this leg does the same job as the top tether point. However, the support leg is not compatible with every vehicle, and cannot be used in conjunction with floor storage compartments.

For ISOFIX seats with a top tether, there are not so many constraints. Providing the ISOFIX seat with top tether is classed as universal, and your cars' ISOFIX and top tether point are approved as universal, you are able to fit the seat in the car.

Top tether seats also tend to take up less room in the car, as there is no support leg in the cab – this can make it much easier for other passengers to get in and out, particularly older siblings who may sit in the middle.

ISOFIX seats with tethers may also be lighter, and therefore quicker and easier to move from car to car, as there is no heavy leg attached to the base.

Finally, ISOFIX + Top tether seats have all the same features and benefits that you would expect, such as easy adjust harnessing, some seats offer longer rear facing, and some even swivel!

Anything to consider?

As with any seat you buy, it is very important to ensure the seat fits every car it will be going into. Not all cars have top tether points, so be sure to check each car. Many ISOFIX + Top tether seats are ISOFIX only, very few have an option belt the seat in the car.