Slide shutter for pinhole/homemade cameras

Okay, I'll admit that I did not print this yet (mostly because I'm some 4000km from the nearest printer to which I have unlimited access). I'm mailing the .obj file to be printed though and hopefully soon I'll have results to show. In the meantime, if anyone would like to try it out, this is a very basic slider shutter for homemade/pinhole box cameras (not very good for curved can ones). After the first prototypes are done I plan on adding a bit to it, specially some way to attach and use a mechanical cable release built from bike's brake cables. This is my first ever attempt at modelling something, 1st time using FreeCAD, and general 1st time in anything 3d printing related beyond sending an image file to the owner of the printer I have access to and letting him model everything anyway he wanted...

To make a better use of the printing time I placed the 2 pieces - both the slider and the slider-channel in the same file but the channel is upside down, since it should keep the slider well tucked between the  "skirts" of the channel and the camera body.

Needless to say, if you'll print this to use in a camera, you should use black plastic, from what I managed to research, either ABS or PLA are ok fro camera building....