This hole is valid when the moon is just rising and also when the moon is very high in the sky. Providing you didn't overexpose, when the film is developed you will be able to measure the angular diameters of both moons with a ruler. When the moon is on the horizon, we see it AND a bunch of reference objects at the same time. Our brains are wired to recognize relative scale, so when we see the moon behind ol' Farmer McCarthy's barn our brains recognize that the moon is distant and hence quite large. The two lines are parallel to each other, and both are straight.
All figures are the same size.
Both rectangles are the same size.