I am a competitive rower with the Potomac Boat Club in Washington, DC. I recently copied a piece of gear that we use in the boats. This plastic part is used to set the spacing of the oar blade with respect to the center of the boat. Switching to smaller boats (4 man from 8 man) requires moving the handle in a bit closer to reduce resistance. I measured the original piece (orange) using a caliper. I drew it up in Autocad and imported it to Blender. There I extruded it to make a 3D mesh and exported to an STL file. I then fed this to Pronterface and printed it. The yellow object is the copy.
The copy works fine. I did notice that in the upper corners there are signs of stress in the plastic. If I re-print this part, I will round off these corners a bit.
G. P. Le Sage Blog 