Jerry-rigged flatbed?

I needed to move 72x80" double doors today and ended up using three 4x4x8' (I needed the 4x4 for another project, rather than just 2x4s) across the tops of the bed walls then cargo strapped everything down. It worked really well, and got me to thinking about a less 'on the fly' solution, like maybe some sort of toggle clamps in the rails that go up through three boards across the bed walls.
Has anyone done anything like this? I mean, it'd probably only hold a couple of hundred pounds in total, but sure would make moving some things MUCH easier.