Warning:

Do not use a seat belt extender. If a seat belt extender is used when
installing a child restraint system, the seat belt will not securely hold the child restraint system. Use of a seat belt extender could cause death or serious injury to children or other passengers in sudden braking, swerving, or accidents.
Attach the child restraint systemto the anchors properly. When using the LATCH anchors, be sure that there are no foreign objects around the anchors.
Also, the seat belts should not be caught behind the child restraint system. Make sure the child restraint system is securely attached. Otherwise it may cause death or serious injury to children or other passengers in sudden braking, swerving, or accidents.