This mod fixes getting shot through walls. That's it. If you expect an essay, then I'm going to let you down.
If you are still unsure what this does. Let me give you an example;
Green Bridge stairs (the ones near the exploded part), normally cops on the lower part are able to shoot through the ground. This mod ensures that doesn't happen.
Now as of version "1.1", it should work for all clients when the host has the mod.