It is to release the tow hook..
When you press the button the tow hook is release and you can pull it into place to lock it.
When you press again the took hook is unlocked and you can push it back up into it's hidden position.
When you press the button the tow hook is release and you can pull it into place to lock it.
When you press again the took hook is unlocked and you can push it back up into it's hidden position.