A small tested and working handcuff key.

I've used the normall (auto) support setting with a threshold angle of 12degrees. This way it only secures/sticks the bottom part better to the build plate. And is just minimum support structure needed for only the first part with the “tooths”. To prevent failing overhangs here.

After printing carefully remove the support material, which should not be verry hard to remove. And be sure the inner tube is cleared from support material. It should snap out with a bit of prying (see picture).

The key in the image is printed with Bambu Lab Basic PLA. Although it holds up pretty well by opening a few times, I would recommend using PETG or a nylon based filament. PETG would just be fine, because PLA might be a bit brittle and snap off on the layers after repeatedly used. But as stated, PLA should just work fine too for occasionally opening.

It should work on handcuffs from Lips and S.P.E., which are quite commonly used in Europe. Probably also working on other used European brands/ types. Handcuffs in the USA/ Latin America in general have different keys.