“Even so,” said Vimes, in the same dreamy voice, “this map will work for thousands of years. It doesn’t mark a rock or a hollow or a cave; it just marks a spot. I can pinpoint it. That is, if I had a pin.”
“I have one!” Sir Reynold said triumphantly, reaching to his lapel. “I spotted it in the street yesterday, and of course hwe all know the old saying: ‘See a pin and pick it up, and all day long’–”
“Yes, thank you,” said Vimes, taking it.

– Sir Reynold, the last pinhead who hasn’t switched to stamps | Terry Pratchett, Thud!