ratchet3.stl is a one piece ratchet for small Allen wrenches, and then you print adapters depending on the wrench size.

ratchet6.stl has 6 inner blades instead of 3, and they are a bit thicker, try it in case ratchet3.stl wears out too fast and no longer locks.

One side is used to screw, the other side to unscrew.

Here is a video showing both:

I printed the ratchet itself at layer 0.2mm, 50% infill, with PLA
I tried PETG, works well too and may be more robust.

The adapters should be printed with 100% infill to reduce breaking risk. Ideally they should be printed flat, so that layers are perpendicular to effort, but I hate supports. So I broke a few.

This is to be used with small allen keys, from 2mm to 5mm like you often use in electronic devices.