This is NOT a part I have designed. This part was on grab cad and I think many of your may find it useful like I have so I will post it here. The original creator is Josh Scheringer and you can find his design on GrabCad by searching "3D Printable Latch V3".
Here is his description posted from grab cad.
"Okay, got all the kinks out now this is the third time I've had to post this. A 3D printable latch with .6mm clearances to avoid welding of parts. I have not done a test print but have gone over this several times and believe its good to go. to print, use the EZ Print.stl as there are NO CLEARANCES between the marble and base, or latch and hook in the step files. This is my first 3D printed moving part so any input is welcome!"
I am printing it right now on an ultimaker 2+ and will let everyone know how it turns out.
supports are critical to avoid bonding