This will slide on 5/8" sail track to act as a stop to keep the lowered sail from falling off the track. It will need a 1/4-20 setscrew. If the printed threads are too tight, you can easily run a tap through the hole. I needed this for my CLC Pocketship sailboat.

BTW, the setscrew in the photo is not 3D printed - I just happened to have it lying around.

Anet

A8

No

No

0.2mm

25%

Make the walls extra-thick. Print with the threaded hole horizontal.
No support needed.