All this talk of manhole covers reminds me of my driving days when I was in the yard with Dave when Charlie`s wagon pulled in with a VERY high load.
As Charlie got out of his cab, Dave said to him "My god, Charlie that`s a high load you`ve got, what is it?"
Charlie carried on to the office, saying "Oh, it`s manhole covers".
Puzzled, Dave thought, No Way could it be anything heavy so went over and pulled the sheet up to reveal rather a lot of sanitary towels.
See you in the dungeon, no.knowledge!