I was riding the shoulder of a divided highway and had an instant blowout. My front tire was sliced all the way across the tread. I made a boot of a couple dollar bills, put in a new tube and rode the six miles home.
Curiosity got the best of me and I drove out to the scene of the flat. Walking the shoulder I found ten box cutter blades intact and the pieces of several more. Had I not picked them they could have caused many more instant flats.