at rikers island jail, a bakery churns out nearly 90,000 loaves of bread per week while teaching inmates how to bake. in many of the prisons profiled on "lockup," inmates have opportunities to learn skills that can help them find work on the outside. but all too many spend their time honing skills more suitable to mayhem and murder. >> i stabbed an inmate 12 times over some dope in front of the chow hall. >> i took a knife and stabbed him with it three or four times until he was dead. and then i butchered him with it. >> you find a piece of metal or something, file it down on the concrete. it ain't got to be sharp, it's just got to have a point. put your handle on it and do what you need to do. >> "lockup" crews are regularly exposed to the tools of a deadly trade. >> every prison we film in, there's always a shank museum, a place where the authorities display all of the weapons that are confiscated by staff. homemade weapons the inmates have made from bed springs or melted down plastic. they're truly ingenious but deadly as well. >> at california's san quentin state prison, we saw how s