Speaking of nuts and bolts, my favorite gaff happened at Cal-Trans.
Hardware for a section of freeway had been put out to bid, and the
bids came back outrageously expensive (yes, even for Cal-Trans).

It turned out that, to save time, the engineers making the drawings
had simply reversed one side for the drawing of the other side.
This was fine, insofar as the two sides were identical.  But the
drawings included nuts and bolts, which the engineers didn't think
about.  The outrageous cost came from making all the left hand thread
nuts and bolts.

Luckily the mistake was caught before production started.

Mike in Sacto