Summarize:

Pens that are made completely from plastic will melt if you attempt to smoke, so the metal tip is important to prevent the plastic from melting in the heat. Take the pen completely apart to obtain the metal tip and hollow shaft of the pen. Unscrew the tip from the pen. Remove the writing tip, ink chamber, and spring mechanism. Remove the back end of the pen. Insert the narrow end of the metal tip into the hollow shaft of the pen. Push it in as far as possible to create a seal between the pen and the metal tip. You can use a lighter to melt the plastic slightly to force the tip to bind to the end of the pen. Place a small amount of smoking material in the pen tip carefully to avoid breaking the seal between the pen and the tip. Breathe in through the end of the pen while you light the smoking material contained in the metal tip.
Find a pen with metal tip. Disassemble the pen. Place the metal tip in the pen backwards. Fill the metal pen tip with smoking material. Light the smoking material and inhale.