I've just spent ages lining up a folder viewfinder so what I see through it is what appears on the film. This is an albada type, folding, 2 lenses, and after using ground glass and focusing screens I thought what a lousy way to compose a pic - the lenses distort, the white line vanishes in a pale sky, and in framing up it was miles out. So I taped some tracing paper over the film gate to get an image and set aboul lining up the white lines to that image. It was quite a way out top and bottom and the viewfinder had to be raised about 2mm along its back edge. I also made a window out of black electricians tape on the front, large lens piece to block out anything that wont appear on film, making composing much easier.
Mine is an Ensign Selfix 820 and I love it, but I do think these folders are let down with toy like viewfinders.