it was the question of an angry user in some lenovo forum, with a closed threat so i can not even answer on it, here is the answer:

lenovo t440 with this symbol on the spacebar you can press Fn + Space to switch on (level1, level2, off) keyboard background lighting – your lenovo has no such symbol?

you can try it anyway but i guess you are out of luck and your lenovo laptop does not have keyboard background lighting (very sorry, it is really a cool locking feature, all lenovos should have these)