I never actually got them to organize stuff, but to house my bunny. House rabbit people use these grids to construct all sorts of sturdy and amazing cages that far exceed the availability in your local pet store.
Here's my bunny in his cage as well as my cat, Simon.
Since we are doing cat pictures all of a sudden, here's another view of the cage and my other cat, Zoe.
I pieced together the bunny cage and my grid using regular zipties.
Now for the attaching part. The downsides of a steel trailer are weight and rust. The upside is that anything magnetic sticks! I have multiple magnets, they hold up my organizer on the door, a tack hook rack, and even my broom. I use these 65lb hooks from Master Magnetics. Careful when attaching these, they are VERY hard to remove and do a great job at holding heavy things. If you have an aluminum trailer it's a little harder because you need to get your grid welded on.
Here's the finished project. I don't have the right stuff in the right baskets, but you get the idea.