their contraband in there. >> hiding anything in jail where every area is subject to inspection at any time takes determination and creativity. just ask marcelo cardenas. >> this is one of the spots that we use for -- to hide the guns, the tattoo guns. i'm just right now making one. >> cardenas, who is sharing his secrets because he is soon leaving for state prison and says he is not worried about punishment, has a clever technique for hiding his homemade tattoo guns. the process begins with another piece of contraband. a box hinge. >> this is my tool that we use to break the wall in by literally scratching it. >> in this case, since the hole is still small, cardenas demonstrates how he uses a bar of soap to conceal one of the magnets used in his guns, rather than the gun itself.