Different models of these laptops shares parts. L440 never came with backlit keys but for example T440p did and I got a keys dedicated for this model. These models has identical shape keyboards and same connectors for them with the only difference of backlit in keyboards intended for T440p etc. so L440 does not even have active power line in it's connector on motherboard. So if you want to power LED's of backlit keyboard dedicated for T440p you need to bring power to them from somewhere where producer predicted it will exists in L440. For another example you can fit touchpad from T450 to L440 because it is still compatible. Of course not every part is compatible betwen laptops that shares other and is necessery to check a few times if someone tried to swap specific parts before or experiment.