One must be slightly smaller than the other so it can slide snugly inside (e.g., a large and small soap box, or two A3 sheets rolled into tubes).
Creating a pinhole camera using butter paper is a classic science project that demonstrates the fundamental principles of optics. Instead of using a glass lens, this "camera obscura" uses a tiny hole to project an inverted, real-time image onto a translucent screen.
To make the interior light-proof and prevent reflections. A pin or needle: To create the tiny aperture (the "lens"). Tape and scissors. Step-by-Step Construction