The Britax Marathon car seat is designed for both rear and forward facing placement. The rear position is for children from five to 33 pounds; forward is for those up to 65 pounds. You can install it with the seat belt or the LATCH system, but the maximum weight for LATCH is capped at 48 pounds.
Place the Marathon in your vehicle in the fully reclined position, facing toward the rear of the vehicle.
Open the rear-facing lock farthest from the buckle.
Pull the vehicle belt through the rear facing belt slot.
Pull the seat belt strap around the buckle strap and pull it out through the second belt slot. Buckle it.
Press the restraint against the seat and remove any slack remaining from the lap portion of the seat belt. Close the lock-off arms on the Marathon to ensure a tight fit.
Place the Marathon in the completely upright position facing forward.
Pull the seat belt up and over the LATCH bar, through the forward facing belt slots and over the LATCH bar.
Open the forward facing lock-off located on the far side from the buckle and remove all slack in the lap belt.
Pull the shoulder portion of the seat-belt as tight as possible while kneeling on the child restraint.
Rotate the lock-off clip upward to lock the seat belt into place.
A car seat can only be effective if it is installed and used correctly in a vehicle, whether forward or rear facing.