The wrt160nlmod.sh script is a setup script for the WRT160NL router to make everyone's life easier! :)

It is available via http://wrt160nl.org/files/wrt160nlmod.sh

Once you have DD-WRT running on WRT160NL, and USB services are all enabled, your ext3 pendrive is connected, just wget the script to the router, make it executable (chmod +x) and run the following command

./wrt160nlmod.sh initiate

You can also use other switches, enter this for the list
./wrt160nlmod.sh

to find out what are those.

If you need more information or a step-by-step guide, check the full description in the tutorial.