I was trying to copy/paste a weapon rack to create a line of them in the cell, but they do not work in game. I tried finding a video or some instructions about how work with them, but have come up with nothing. Does anyone know what to do? I had the same problem with bookcases, even though I copied what I thought were the activators attached to them.

Just go to the WarhousePrefabs cell and copy it from there. Make sure you copy the markers too. Easy!

Here's a video if you want to learn how to make them yourself. http://www.youtube.com/watch?v=qGdfilJ12l0

Cool. Thank you two for your help! Now I can have the house I aaaaaaalllwaaaaayyssss dreeeeaaammed of.

And goodluck!
I never could get the warehouse versions to copy.
I recommend you save a backup and test - it set me back a month when most of my activators mysteriously got transported to the warehouse cell.

I ended up following the tutorials and making them from scratch and they work like a charm.

I've finally got the hang of copying the entire collection but they are still very inconsistent. I finally just deleted a couple from my house because no matter where I copied them from they acted wrong and it seemed to be more related to where I pasted them rather than where I copied them from. The wall space behind the first bookcase inside the front door of Breezehome. The long wall, between then corner column and the next column. No matter where I have copied it from it always flips the sword around 180 degrees but keeps the handle in the same place so the sword sticks out way over the end of the plaque. That's just one example. It doesn't matter if I copy the original above the door or one of the MANY successful copies I have made and placed around the room.

Sounds like the rotation bug that affects plaques and racks, and sometimes other activators. Try a less round number for the Z rotation value for both the static object(s) and the activator(s). For example, instead of 90, use 89.9; instead of 180, use 179.9; etc.