Are you familiar with the word "submarine"? A submarine is a kind of boat that moves underwater. Submarines are common crafts for the Naval forces of any country. But, while moving underwater, submarines need to know where they are with respect to other objects on the surface of water. The device they use to do this is called a periscope.
Periscopes are optical instruments that can afford submariners a limited though vital visual picture outside their windowless hull. Traditionally, periscopes offered the submerged submarine its only glimpse of the outside world. Classic English war movies have also made them the submarine's most familiar feature.
For most of us, who are unlikely to come across submarines in real life, a periscope can make it possible to see round corners and over the heads of crowds during processions or at sporting occasions. In a periscope, two mirrors are arranged at 45 degrees to each other. One mirror captures the rays of light from the object, and then they are passed down the tube to a second mirror which directs them into the eye. The use of two mirrors means that objects are viewed the right way round. Each mirror reverses the image and this results in a corrected image in the bottom mirror.
So, all you need to make a periscope is a long box or tube, and two mirrors.
The long tube or box is rather easy to get or make. If you are ready to spend some money, you can easily buy PVC tubes from a hardware store. But, even when you are not ready to spend too much money, you can easily find such long boxes/tubes around you, for example you can use cardboard cartons on sherbet bottles, corrugated boxes used for supplying fluorescent tubes, you can use tubes used for tennis balls or shuttlecocks and so on, there are many options. The last but not the least viable option is to make such a tube your self. You can make it from a cardboard sheet, or from disposable paper containers used for cooking oils, fruit juices, milk etc.etc.
Many people have described in detail, the method to construct a periscope, using any of the above options. Below is a list of addresses of such WebPages and that can help you according to your need and choice
The more difficult part, as you may discover, is to get the two mirrors of the right size. Aluminum foils/sheets, or the reflecting surface of many disposable bags of food items can be perhaps used instead of the mirrors, but unless you are very lucky there reflectivity is seldom as good as that of a glass mirror.