Overview
This is a little trick to turn a simple prison "safety" pen into a one-time use stabbing weapon or "shank." This is a useful tool if you happen to be sharing a prison cell with any script-kiddie / sell-out computer hackers, and desperately want to put them out of their misery.
Remember: Real computer security consultants don't spend five years in jail.
Example of a prison pen and its components:
These style of prison security pens are just the ink tubes from regular "click" pens, but with the outside case replaced with a piece of 1/4-inch flexible rubber tubing. Two 1/4-inch end caps (one with a hole in it for the tip to poke out) complete the pen. The idea is that the soft tubing will reduce the chance of the pen being used as a stabbing weapon.
Now, to turn the pen into a stabbing weapon, all you have to do is somehow strengthen the outside case of the pen. The easiest way to do this, with the limited materials available, is to tear a sheet of paper in half, and very tightly wrap the flexible tube in it. Wrapping the pen case in paper will significantly increases its strength.

Example of how to wrap the pen case with a torn sheet of paper. You should remove the pen's end caps, and place the pen along the smooth edge of the paper.

Example of rolling. You'll have to pull the paper very tightly for this to work. Practice if you can. The end with the tip sticking out should be used as the stabbing tip.

Die Motherfucker Die!
It works pretty well, but it's only a one-time shot as the paper will unravel.