For the unaware, the Lenovo keyboard placement of the Fn and Ctrl keys looks like the following.
For the longest time, this bothers me because I grew up expecting the control key to be at the corner of the keyboard.
So when I got the x240 a while back, I was pleasantly surprised that they finally added the feature to allow the swapping of the keys. To access this, boot into the Thinkpad setup, and select Config -> Keyboard/mouse -> Fn and Ctrl Key swap.
To my surprise (and horror), I find myself consistently hitting the wrong keys after enabling the option. It seems Lenovo has trained me to treat the corner key as Fn when I am on a laptop. And since I use the lenovo laptops 95% of the time, I boot the BIOS backup to disable the option.