This is a replacement for the old-style Sunfish deck drain plug, made to fasten/loosen with a quarter.  It has a hole in the bottom for a Stainless Steel Ball Bead Chain 3.2mm / 1/8" like the original part. It goes in snug, and a hot soldering iron can be used to permanently capture it (see cover image).

Recommended print orientation: standing straight up, thread at the bottom.

No supports needed

Printed and tested with 0.6mm nozzle, 0.2mm layer height in PETG, with 25% infill in 3D honeycomb pattern.

Updated 2025/04/01:

Added source ipt and step files.