notice how the cabinets look kind of...off? that's because the drafter hired to do these diagrams tried to draw using linear perspective, but apparently didn't know how.
linear perspective is a system of drawing used to create the illusion of 3-dimensions on a 2-dimensional surface, rendering objects as they appear to the human eye according to geometric rules. for example, we see parallel lines as converging in the distance, although they really don't. (think railroad tracks...the tracks look like they get closer together in the distance, but we know they are actually parallel.)
objects viewed head on should be rendered using one-point perspective and objects viewed at an angle should be drawn with two-point perspective. one-point perspective has one vanishing point at which parallel lines converge, and two-point has two vanishing points. (it's a pretty simple concept.) here's a diagram...
(click the image for more detailed instructions.)
our buddy drawing the medicine cabinets needed two vanishing points, but has none. his parallel lines don't converge, leaving his drawings looking...well...amateurish.
he should have paid more attention in art class.