Related:

• Ano-fossal ambiguity (can't tell his ass from a hole in the ground).
• One who does not know a burro from a burrow does not know his ass from a hole in the ground!
• Tact is the ability to tell a man he has an open mind when he has a hole in his head.
• Carefully study these two enlarged photographs on display, Mr.
  Rafferty," the attorney for a politician suing a newspaper for libel instructed his client on the witness stand, "and indicate which is your ass and which is a hole in the ground....
• I tripped over a hole that was sticking up out of the ground.
• He only knew his iron spine held up the sky -- he didn't realize his brain had fallen to the ground.
  -- The Book of Serenity...