Rectangle
The rectangle, in relation to the square, can be regarded as a “disturbed” or unbalanced mandala (or symbol of wholeness), corresponding to numbers like three and five, while still incorporating the ordering principle of the number four. If horizontal, it suggests that consciousness predominates (it lacks depth); if vertical, it suggests that the unconscious predominates. Horizontal forms are associated with the rational functions (thinking and/or feeling) in Jungian typology.
Horizontal and Vertical
What distinguishes the rectangle from the square is that it extends either horizontally or vertically (at least typically), which makes it “disturbed.” The horizontal suggests a structure grounded in reality, relating to the dreamer’s interactions with others and her social life.
The vertical, on the other hand, pertains more to a I-to-I relationship, such as between the “lower” self and the “higher” self; often connected to spirituality but also, conversely, to the underworld.
The horizontal rectangle is linked to reflection, while the vertical rectangle is tied to emotional experience.