First of all, you will need all of the things shown in the picture. Get them together.
This gun is a moderately powerful K'Nex gun, which I made to be as small and portable as possible. Enjoy!
Step 1: Build Barrel
2. Add a red connector with a green little rod in the middle slot. Put a yellow rod on the other slot, as shown in the 2nd picture.
3. Add two more grey connectors, as shown in the 3rd picture.
Now move on to building the firing rod...
Step 2: Build Firing Rod
2. Add the firing rod to the barrel, as shown in the 2nd picture.
Now move onto attaching the rubber bands...
Step 3: Attaching the Rubber Bands
Enjoy your moderately powerful darrenger!
Notice: This gun has an auto-safety mechanism if you put the rubber bands on the way it is shown in the picture. This means that when you pull the firing rod back the appropriate length, it should lock into place.
Other than that, it is a simple K'Nex gun.