What is the LockStrong belt tensioner and how do I know it's properly closed?

The LockStrong is a belt tensioner used to secure the vehicle belt or LATCH/UAS strap during installation. When fully and properly closed, the Belt Lock Indicator turns GREEN. If it does not fully close and the indicator remains RED, open the LockStrong and try loosening the belt or LATCH strap slightly before trying again. Never place the vehicle belt over the LockStrong, as this prevents proper operation of the car seat. (Pages 60, 71, 81)