A simple last-minute design for viewing an eclipse and avoiding eye damage.

Requirements:

• An empty toilet paper roll (41 mm diameter - OpenSCAD source included for modification)
• Aluminum foil (or some other thin, opaque material)
• Tape

Print the top cap, and tape a piece of aluminum foil with a tiny pinhole (as small as you can make) over the circular hole. To make it look neat you can tape it inside the cap, but outside works too. This will go on one end of your TP roll.

Print the bottom cap. You can print it in white with ironing for a smooth surface, or use any colour and put a circle of paper into it.

Cut an opening in one end of your TP roll to allow you to see the projected image. Put the bottom cap on this end, and line up the open part of the cap with the cutout you just made. Put the top cap over the other end. 

The top cap should fit snugly, but the bottom one may need some help with tape.

To use it, go outside and point the top toward the sun. You should be able to see the image through the window at the bottom. My picture is just looking at a light bulb indoors, because it was cloudy. Happy viewing!