click and snap system vol. 1

i tried to design some simple parts which could click into eachother easily but also are robust enaugh to last several assemblys/disassemblys...
i see them more as a practice in designing moveable 3d printed parts, but i thought you might find a practical use in them, or use them as inspiration or template to create/remix something useful out of them
i already printed a handful of parts and they work surprisingly good in my opinion :)

January the 22nd 2018:
I've just added a new part in 2 variations, to mount on flat surfaces by using glue or screws and 3 new variations of existing part

still January the 22nd 2018:
added 3 cross-pieces