This extrusion kit will allow you to add a Front-to-Back bar that runs the length of your rack on the inside, with a parallel orientation to the bedrail. (Not at an angle). This creates a mounting surface for which drawer slides can be mounted to, or simply serve as an additional low mount side bracing, custom bottom surface and more.
Choose the Bracket Type based on the rack you have. (9D is for Gladiators, 13D is for Softoppers, except Gladiators, 20D is the standard angle).