Test your child's seat by pulling it forward and sideways. If the base moves, use a different seating position unless your vehicle owner's book shows you how to make the belt system hold a child safety seat securely. A tether may help. It may be the only way to keep a safety seat secure if belts are anchored forward of the seat back. A tether aids protection even when the safety seat is held firmly with the lap belt.
Some manufacturers have tether kits for their forward-facing safety seats.
Do not attempt to install a tether on a safety seat not made to use one. Many vehicles have holes drilled behind the rear seat to hold a tether anchor. Some have nuts installed. Check the owner's manual for tether anchor locations. This special clip is available only from Ford, Toyota, and Nissan dealers.