The most common weapon inside is simply a can top. Pulled off a tin of beans and folded over, it doesn’t even need to be sharpened to leave a jagged scar. A shank, also known as a shiv, is not for cutting but for stabbing. It’s called a “gun” in jailhouse vernacular, and the most valuable kind is fashioned out of materials that don’t activate a metal detector. Prison armorers make a good living shaping brass (sourced from structural elements) and aluminum (soda cans, mostly) into knives, though fiberglass and even wood can work, too. Most shanks are made for one specific purpose and disposed of immediately thereafter; getting caught with one is a year in solitary.
Most of the way through the piece, there is an interesting meditation on the ramifications of violence which does apply to your writing. And, of course, a fairly detailed look at improvised weapons in prison.