You may be able to find small mirrors at a craft or art supply store, or from an online store.
A long, sturdy cardboard tube could also work. You could use a large, flat sheet of sturdy cardboard instead. Lightly score it with a craft knife to divide it into four sections, then fold it into a box and tape together. You can use two sturdy paper boxes. Or stick several layers of recycled toilet paper together to make a sturdy base. You can even use shipping paper.
You can tape two tubes or two homemade cardboard cartons together in the same way, to make a longer periscope. However, the longer the periscope is, the smaller the image will be. [2] X Research source
A craft knife may be the easiest tool for cutting the hole, but should only be used with adult supervision, as it is very sharp. If you are using a cardboard tube instead of a milk carton, flatten it slightly so you can trace the mirror.
To test whether it’s at a 45º angle, use a ruler to measure the distance from the closest corner of the carton to where the lower edge of the mirror touches the carton’s side. Then measure the distance from the same corner to the opposite end of the mirror, where it touches the carton’s top. The two distances will be the same if the mirror is angled at 45º. Don’t use glue yet, since you might need to make adjustments to the mirror’s position.
If too much light is coming through the “eye” end of your periscope, making it difficult to see the reflection, tape black construction paper over the outside edges of the hole.
You can find PVC pipe at a hardware store or home improvement store.
