(Debian - Etch - KDE)
I've installed "secure-delete" and it comes with a script with instructions which say: "You should run this in the STOP runlevels 2 and 3". It's supposed to wipe RAM (smem), swap (sswap) and fill sector empty space (sfill) sometime during the shutdown process to clean out the system every time it shuts down.

Also, instead of running the entire script, each program can be run on its own (i.e "smem") in which case the instruction is: "Just put this in the late run level of the STOP part of rc2.d".

I know "S" is for "start" and "K" is for "stop" and I'm supposed to put the script itself in the /etc/init.d, then "symlink" it in /rcX.d. I've put these scripts in so many places and run so many commands that now I get blank screens and crashes and I have no clue what I've done.

Would someone be so kind and write step by step how to add a "myscipt.sh" to the LATE part of the shutdown sequence. What does "late run level" mean (K92 is later than K20... correct?) and what is the "stop" part? I've read codes and seen lines like "...start)" and "...stop)"... Do I add it in that section?...Thank you so much.

Yes K92 would be later than K20 (K99 would be the last script to be executed) and K is for 'Kill'.

If I remember correctly with Sys V style scripts on Debian-based systems you are supposed to use update-rc.d to manage your startup scripts. But yes, the basic idea is that the script will go under /etc/init.d and you will have symlinks pointing to it from directories (/etc/rc?.d) corresponding to the runlevels you are interested in using the script.

It might be helpful if you post what you currently have in /etc/rc?.d and /etc/init.d. Do a ls -l so we can see where the symlinks point to.

The actual script should have stop and start sections and these are called as needed. You don't need to write these.

This page about debian runlevels may be helpful to you.

Sorry this isn't a step by step how to, but I don't know the current state you are in and I am not currently using sys V style scripts (I use BSD style - much simpler in my opinion).