They key detail is to check the hook at the bottom. The lock cover must be pressed firmly UP to retract the hook, which allows for installation and removal. It must be pressed firmly DOWN to engage the hook after installation and prevent removal (you MUST press down and hear the hook engage, or the crossbars could disconnect from the vehicle while driving). Just listen for the click when the hook moves, and then make sure they are fully attached before driving.

Locking the crossbars with the key does not hold them in place, it only prevents someone from pressing firmly up on the lock cover to remove them.

This video is for informational purposes only. It is the user's sole responsibility to ensure the crossbars are firmly attached.