My Lenovo T420 has two keys above the arrow keys that I almost never use. By default they are forward and backward keys for browsing the internet. I decided to remap them to End and Home. This isn't too difficult.
To do this simply use the following terminal commands:
use xev to find the keycode for the key you would like to change the mapping of
use this link to find what you want the key to actually do
Use xmodmap to map the two together.
xmodmap -e 'keycode 167=End KP_1 KP_1 End'
xmodmap -e 'keycode 166=Home KP_7 KP_7 Home'