I bought a 3 axle flatbed trailer that i use to transport my tractor and implements and pick stuff up for the farm. It has a capacity of 12,000lbs, and is 8' wide and 20' long. It's been really great to have.
The side rails on it aren't very sturdy. It's a piece of angle iron, with stake pockets welded every few feet and a piece of flat stock welded on top of that. the theory is that you have a continuous rail along the edge for tiedowns -- but in practices it's not sturdy enough to do the job. In the picture above you can see it's been smooshed out (I was unloading the trailer from the other side with a forklift and the fork caught the edge and pushed it out, and then the strap I'm using in that picture is lifting and twisting it, too. Just not really something that inspires confidence.