INSTRUCTIONS:
All downloads contain .img files bootable through Fastboot.
Make sure your device is in Fastboot mode (you get there by holding VolUp+VolDown+Power when the device is turned off), then run the included script for your OS. On Linux and Mac, you may have to chmod +x root-linux/mac.sh before the script does anything.
A special boot image will load, which will install (only) SuperSU, then reboot into Android.
UNLOCK BOOTLOADERS:
The included scripts perform an "OEM bootloader unlock". If this fails, the root will not work. If it succeeds, and you were not previously unlocked (first time rooting), it will probably wipe your data! As I always say, please BACKUP!
For some device (Sony, Verizon, etc) you may need an OEM-specific tool to unlock the bootloader. Please do not forget to check and use this tool, if provided by your specific manufacturer.