Not seen: a group of 12 men blowing their darnedest into the duct.
From the submitter:
The CPU fan on my computer broke. The screw holes of the replacement fan did not match up with the old screw holes in the heat sink (there were notches cut out of the corners, there was nowhere to screw the new fan to). I had to find a way to make my own screw holes for the fan, without impeding air flow.