The rule of thirds is a compositional rule of thumb in visual arts such as painting, photography and design.[1] The rule states that an image should be imagined as divided into nine equal parts by two equally-spaced horizontal lines and two equally-spaced vertical lines, and that important compositional elements should be placed along these lines or their intersections
Rule of 3rds on that pic is the 3 verticals of the shed and gate aswell as horizontal using the slats on the shed.