I'm looking to put a Dee Zee or Titan poly tool box in the back of my Silverado. Do either of these have D-rings or some place to tie them down so they don't slide around in the bed? I don't care about security as I'll take out the box when I'm not using it. I have a cargo bar I could put across the bed, but I'd rather tie it down with straps. Anybody use these poly boxes? Thanks!