Here's a 3D-printed version of the classic impossible dovetail puzzle, inspired by a machined metal version by Chris at Youtube channel Clickspring.

After modeling the geometry in Onshape, I printed my version in Estonian blue, black, and white. I wanted to sign my name on the pin so I rebuilt that part in Solidworks, which still offers a less annoying way of importing 2D vector art for this sort of feature. If you'd like to make your own impossible dovetail or play with the CAD models, follow these links:

• Impossible dovetail, Onshape document
• Impossible dovetail pin, Solidworks file
• Impossible dovetail, STLs for 3D printing