Disclosed herein is a system for securing a base of a child car seat in an associated vehicle using a safety belt of the associated vehicle. The system comprises a base configured to support a seat of the child car seat and a belt lock off mechanism. The belt lock off mechanism includes a first arm movable between (a) an unlocked position in which the first arm is not configured to tension the safety belt of the associated vehicle, and (b) a locked position in which the first arm is configured to tension the safety belt of the associated vehicle. A second arm of the belt lock off mechanism is configured to engage with and urge the first arm to move from the unlocked position to the locked position so as to tension the safety belt of the associated vehicle.