Any camera is basically a light-proof box, with a lens on one end, and a place to put film on the other. A Pinhole, or Lensless Camera executes that principle to its ultimate end.
Lensless Cameras are constructed of different woods. Each model has a tiny hole (1/64" or smaller) precisely drilled in the front panel. The shutter is simply a small hinged metal plate that the photographer swings up and down to begin and end the exposure. The imitated focal length is determined by the length of the camera. The format is determined by the size of the back of the camera, which accepts the film holder. Since it is designed to accept a sheet film holder, there is no need to load the camera in the dark.
This is a Baltic Birch, 4 x 5" Pinhole Camera, with a focal length equivalent of 225mm, which is a telephoto lens for this format. Average exposure in bright, noon-day sun is 4 seconds, using 400 ISO film.