This model is a recreation of an aluminum RMP Backer from Greyman Tactical, it's used to mount attachments to their panel system.

Pretty simple for PLA or PETG 100% fill.

The 100% infill is essential because, when mounting items, you'll either need to screw directly into it or drill and tap a hole. With a solid fill with no predrilled holes, you have the flexibility to position your hole precisely where it's needed.