jludwig, those words are SO true!!
I had an Engineer try to tell me how to weld once. I said, "Well, if your way is so much better, here's the helmet and gun. Show me how to do it." His reply? I don't know how to weld....
Same guy would say "Here's my idea. Can you build it, and draw me a dimensioned sketch? I'll turn it into a print."
Ok, sure............. NOT!!!
Same guy would draw parts and assemblies but never check for interference fit. Not good when the parts have to be made from aluminum extrusions and extruding molds aren't cheap!