My laptop keyboard is little annoying – it have a Print Screen(PrtSc) button between my right control and alt keys – usually around that area you will find the windows(super) key, so I wanted to remap it, when i am using i3wm.

So first of all you need to make sure what is your key “called”, you can to that with the xev program.

Then you need to get your modifier map with: xmodmap -pm
In my case my output was this:

xmodmap:  up to 4 keys per modifier, (keycodes in parentheses):

shift       Shift_L (0x32),  Shift_R (0x3e)
lock        Caps_Lock (0x42)
control     Control_L (0x25),  Control_R (0x69)
mod1        Alt_L (0x40),  Alt_R (0x6c),  Meta_L (0xcd)
mod2        Num_Lock (0x4d)
mod3      
mod4        Super_L (0x85),  Super_R (0x86),  Super_L (0xce),  Hyper_L (0xcf)
mod5        ISO_Level3_Shift (0x5c),  Mode_switch (0xcb)

I use mod4 for my i3 config, so I needed to add the Print key to the mod4 modifier with this command:

xmodmap -e "add mod4 = Print"

After that we see that Print is added to the mod4:

mod4        Print (0x6b),  Super_L (0x85),  Super_R (0x86),  Super_L (0xce),  Hyper_L (0xcf),  Print (0xda)

And you will probably want to add this command to your i3 config so it get excuted on each boot:

exec --no-startup-id /usr/bin/xmodmap -e "add mod4 = Print"