Three different, fully parametric sets of rigid wrist cuffs. Each cuff is hinged with a printed pin and can be locked with a luggage sized padlock or a hairpin clip. The three different sets are straight (modelled by my wife), wrists rotated 90 degrees, and wrists angled 90 degrees.

If you have fusion360 (and it's freeish for hobbiests!), you can change the wrist sizing, the distance between the two cuffs, and how tall the cuffs are. With these choices you can completely customize the cuffs to your size. You can also print them as rigid leg cuffs by upping the size of the wrist holes to fit ankles instead.

If you don't have or don't want fusion360, I included 24 pre-created STL's in the following four wrist sizes:

1.75x2.25 (my female model's wrist size)2x2.252x2.52.25x2.75

For the straight cuffs there are 3 lengths, 1/2 inch, 2 inch (as pictured in use) and 5 inch. For the wrists rotated 90 degrees, there are two length options, 1/2 inch and 3 inch. There's only a single length for the wrists angled. Each of the length options comes in the four wrist sizes mentioned above.

You'll need to print 7 total pieces - 2x each of the hinge pin and locking pin, 1x CuffArm, and 1x CuffSwingL and CuffSwingR (these pieces are identical, just reversed - but printing them reversed means the surface finish will match when you put the cuffs together). For the wrists rotated 90 degrees, there are two cuff arms that must be epoxied together to create the finished product.

I recommend printing with full supports, and print the pins with 4x walls in good infill (50%) to keep them strong. If the intended recipient is a struggler, you will probably want to go for the same settings for the cuffs themselves too.