The next time you need to clean the gutters at home and don't want to get the ladder out, try standing on the NFL rule book.
The PDF version available for download at the league's website runs "only" 104 pages, but don't fret. The rule book is already so dense in spots it makes concrete seem porous, and it's only going to get thicker. A joke making the rounds even now is that linemen are skipping bench-presses in the weight room and sleeping with a copy on their chests at night instead.
Since nobody was perfect the last time we checked, it's no wonder NFL referees still get it wrong on occasion.