Lenovo YOGA 900S-12ISK User Manual page 8

Chapter 1. Getting to know your computer
Function key combinations
Through the use of the function keys, you can change operational features
instantly. To use this function, press and hold Fn a; then press one of the
function keys b.
b
a
The following describes the features of each function key.
Fn + Esc:
Fn + Space 
(on select models):
4
b
Switches to paper display mode.
Adjusts the keyboard backlight 
(enable  dim  disable).