This mod makes bow and oil attacks from siege defences (towers and gatehouses) have extremely long cooldowns. In other words, you'll only see them happen once per siege unless you sit around for an ungodly amount of time.
Additionally, ballista and cannon attacks from towers only happen thrice as often.
"WHY WOULD ANYONE WANT THESE SETTINGS?" Because the AI is terrible at sieges. This mod gives the AI a fighting chance at taking your settlements. No longer can you station some pikemen at a gatehouse and watch as the AI loses hundreds of men from oil.
"I'M NOT GOOD AT INSTALLING MODS! HAAALP" Download the file called descr_walls.txt and place it in your Stainless Steel data folder. If it asks you to replace a file then you know you did it right. I recommend making a copy of the original file for easy deletion of this mod.