Designed for a 3/8-16" x 1" bolt (and corresponding 3/8" hex nut). I glued the hex nut into the bottom piece for added security (and so it didn't drop down in the side of the bed).

See photos for basic installation process. I printed in PETG but other options like ASA might be better for strength and long-term durability. Infill is fine at 15%, but I highly recommend a significant number of perimeters for strength (I did 8 for reference). I plan on painting them for added UV protection and to better match the bedliner. I didn't load test them to failure on this most up to date version, but pulling from multiple directions didn't result in failure with

Requires support under the hook piece during printing. Would recommend printing in the orientation shown in the screenshot and in the .3mf files for maximum strength.