DISCLAIMER- I take no responsibilty for what you doo with this or any injuries sustainded during construction or use.
Step 1: Materials & Tools
-A BIC mechanical pencil gun.
-A piece of wood.
Step 2: Attaching the Pencil gun thingy.
Step 3: Attaching the PEG to the wood.
Step 4: Cocking & Firing
Step 5: Ammo
You can try to make your own ammo just follow the link Free BB ammo
You can also use anything that will fit in the barrel (though the results vary.