Though about this a few times. I wanted an easy way to load the back of the pickup without having to tie anything down every time I take a car out, yet not lose anything out on the trail. So I came up with these. I cut out a "false floor" from a plastic sheet the, the same shape as the bed floor and painted them black to match the bed itself. I then selected what I wished to carry in the back of the pickup and zip tied them down to the "false floor". 

All I have to do now is choose which one I want to load and place it in the back of the pickup and I'm done  

Nothing is fixed to the bed! Gravity doing its thing  Limited by my imagination