one sided shape
thingiverse
I was messing around one day and created a figure that when you follow its edge, you'll discover it has just one edge.
Download Model from thingiverse
With this file you will be able to print one sided shape with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on one sided shape.