You have two choices for installing a convertible child safety seat in the rear-facing mode: You can use the vehicle’s LATCH (Lower Anchors and Tethers for Children). Or you can use the vehicle’s seat belt. Which is better?
Our technicians found it easier to achieve a secure fit with LATCH. (See our convertible car seat Ratings for the best performers.) Rear-facing installations with the vehicle’s 3-point seatbelt may cause the safety seat to tilt to one side, as the "shoulder" portion of the belt tries to pull upward on the seat. LATCH can avoid this. If your car doesn't have LATCH, you can install the seat using a locking clip, leaving the belt in "unlocked" mode to keep the seat in place.
For more information, see more convertible car seat tricks of the trade.