I designed a simple ratchet joint based on stuff I've found and referenced. The idea is to have sturdy joints for some of the larger figures I'm trying to design. It is a work in progress, but if anyone wants to fiddle around with this version and maybe even give me suggestions, I'd love to hear from you! There are two copies in the stl, because it is intended too be mirrored across models.

ASSEMBLY: place the two parts either facing each others tabs, or at a 180 degree rotation where two small indentations allow you to slot in and pull apart the two halves. This locks the two parts. A 4mm pin can slot into the center for more support (Sorry about that, I use lollipop sticks as pins).

Size: About 25mm x 35mm x 10mm with two 10mm x 5mm tabs

List of pending improvements:

1. Only works properly one way, since my silly brain thought two tabs facing the same direction was a good idea.
2. Gets stuck sometimes, especially if printed wrong.
3. Need to improve the clearances and measurements.

Material: PETG