If you didn’t option your Gladiator with the Trail Rail system, you can still DIY your own cargo management system. Here’s one example by a Gladiator owner who installed his own system using S-Line O-Track aluminum track with tie-downs.
The owner was able to utilize the Gladiator’s pre-drilled holes for the trail rail system by drilling holes in the aluminum track and attaching it using 6MX1 screws (the stock thread for the Gladiator trail rail system).