The double D-ring buckle for strap webbing may not be the quickest to fasten or the easiest to open, but in very easy to make with a 3D printer and here you can download a 20mm, 25mm and 32mm version.

Printing and Assembly

This part is very simple to print. Print it in the uploaded orientation with multiple perimeters (6) and 100% infill for optimal strength. I typically use PETG for functional parts, ASA is another good option if you plan to use the buckle outdoors in direct sunlight. PLA should work as well. Just keep in mind that PLA is not very god for outside use.

To assemble, form a closed loop with the strap, which should be permanently attached to both rings. You can do this with a strap tensioner, as shown in the photos, or by simply stitching the loop together is also effective. Alternatively, gluing the strap with super glue, but you need to use a clamp and allow sufficient curing time.

How to use.

The rule for using double D-rings is simple: thread the strap through both rings, then back through one of them. For a visual demonstration, please refer to the video linked below.

Disclaimer

For my purposes, the buckle has been more than sufficient, but your experience may vary. Use at your own risk.

Video on load testing and usage of double D-rings (Metal)