The picture shows a dollar bill that was inside my tire for a few months under a gash. Click image for larger version.  Name: dollar_bill.jpg  Views: 560  Size: 95.2 KB  ID: 15412

Found it when I had a flat on that tire yesterday, having forgotten it was there. It was folded in thirds inside the tire. Yesterday's flat was caused by a piece of glass, unrelated to the old gash and boot. Was rather surprised at all the rips in the dollar bill. The rips were perpendicular to the direction of tire rotation. I'd guess they happened when I hit bumps with that spot on the tire and the dollar couldn't flex as much as the tire. Maybe dollar bills aren't the best long-term boot. I did put a dollar in a tire on my road bike a couple weeks ago under a 1/4 inch cut, and it removed the slight bulge on the tire so I could ride a 27 mile race without worrying.

Has anybody else inspected old tire boots? What materials have you used? Which ones have held up the best?