NOTE: THIS IS MY VERY FIRST INSTRUCTABLE SO PLEASE EXCUSE ME IF IT SUCKS. I DON'T REALLY KNOW HOW TO MAKE AN INSTRUCTABLE ON HERE..... (also, sorry for bad pictures, i was using my webcam. and the lens i made was a bit blurry.......... but it still worked great) Step 1 is to unscrew an old or cheap nerf attachement. I ttok apart my nerf flashlight. Then You'll need to take out the part that slides on to the rail (the rail mount). Next get a toilet paper/ paper towel roll and cut out the shape of which the lens will fit. After you do that, you'll need to get an old pair of "real 3D" movie glasses and take out the lens. Then, trace the size of the toilet paper/ paper towel tube onto the the lens. What you'll do next is cut out the circle and place the lens inside the tube to where it fits snug. Take some superglue and glue the lens into place. If you don't have any superglue than some tape should be fine. After you're done with this, superglue the sight onto the rail mount that you took out in the beginning. Make sure the sight is facing the right way when you slide it onto the gun rail. Lastly, get a red sharpie (although any color will do) and draw a small circle in the center of the lens. And there you have it, a cheap nerf gun red dot sight!