This is a cheap red-dot scope I made using house-hold materials. The only thing you might need to buy is electrical tape.
Step 1: Materials
These are there materials you will need:
1 toilet paper roll
1 Roll of electrical tape (scoth tape can be used, ut will look much better with solid black tape)
1 Pair of Scissors
1 Sharpie, color of your choice (Red for Red-Dot, I used Green in this one)
1 Saran wrap roll
1 Gun to mount it on (I used my Airsoft UTG MK23)
These are house-hold materials, except maybe the electric tape.
Step 2: Putting on the Saran Wrap
Cut a peice of Saran Wrap approx. 5 inches by one foot and straighten it out. Take the Saran Wrap and cover one end of the tube tightly. Grab the tape (this part is tricky, it took me 3 tries) and secure the tape so it is tight, and not loose on any areas. I then like to cover the entire roll with the tape, just so it looks cool.
Step 3: Drawing the Dot
Take the Sharpie you chose and draw a dot or other crosshair on the Saran Wrap that you put on. I chose a plus and dots. You could also cover the side of the roll with wrap and make a dot on one and a circle on the other, that's up to you. You can also use a ruler to find the exact center, but it doesn't work good.
Step 4: Attachment
To attach the scope, I simply taped the scope to the gun. If you gun is real, a spring airsoft gun, or a gas/electric blowback, make sure the tape stops "on the slide" or you will tape the slide to the gun, which isn't good. Make sure the scope is relatively lined up with the iron sights,and enjoy!