Via Bruce Schneier's blog:
A collection of 11 prison shivs confiscated over 20 years ago in New Jersey.
Think about these, and the adverse conditions they were made under, the next time you see someone's pocket knife being taken away from them at airport security. We can't keep weapons out of prisons; we can't possibly expect to keep them out of airports.
Not entirely unrelated, Prisoners' Inventions, an exhibition of reproductions of objects created by prisoners from the available materials by an incarcerated artist. From paper mache dice to a tatoo gun.