This is a pretty simplistic Shackle, with a functional print in place hinge, if the hinge pin happens to break i reckon it wouldn't be hard to print a new one in two pieces: a sleeve and a peg and glue them into place.

as the model stands there is exactly 0.2mm of space between all moving parts, so make sure your printer is dialed in to prevent seizing of the hinge. I designed the locking pins to take padlocks (may require some modification pre or post print for smaller locks) pins, or rope, i would not recommend printing this in TPU or other flexible filaments as the hinge mechanism will almost certainly seize.

I have printed this hinge in PLA on normal settings with a 0.4 mm nozzle with no troubles on my Ender 3.

If you have any troubles comment below and Ill try to help.

For those who will be using these for rough adult play, i reccomend putting some foam or soft fabric inside the cuff for some greater comfort, if you find yourself wanting a chamfered edge to the cuff i still have the file saved in Fusion and can easily add that as a remix if you'd like to have it.