Step 1: Materials
A BIC Round-Stick pen
A thin rubber band (Any size)
A K'nex grey rod
Step 2: Making the Barrel
2: Rip it out. (no picture)
3: What you have done.
4: What you're going to take out.
5: Stick the K'nex piece in the barrel.
6: Hold it up.
7: Slam it against something hard.
8: That should get it out.
Step 3: Attaching the Rubber Band
2: Cut the small band like this.
3: Wrap it around...
4: Put the tip under of the loops to secure it.
Step 4: Firing
2: Put in the skewer. (Point out)
3: Push the skewer in so you can grab the dull end.
4: Now grab it.
5: Pull it back so that the tip of the skewer is hidden...
6: ...And let go!