What are Interlocking Shapes?
Space division in a painting is more interesting when you create two shapes that interlock, as in a puzzle or jigsaw puzzle.
Example
You can see the negative sky shape formed by the top frame of the painting and the silhouette of the buildings. The houses on the left provide the interlocking shape into the negative shape of the sky. There are also interlocking shapes to the right provided by the sky shape inserting itself into the line of buildings. You can see the puzzle-like piece in green fitting into the contour of the houses.
When designing your space division using interlocking shapes, you also need to take into account unequal space division.
Master Examples
Further examples can be found in works by master painters. In this color study by Turner, you can see the contours of the landscape and vermilion towers create interlocking shapes in the sky. This shows how you can use compositional studies to explore the use of interlocking shapes to strengthen your painting design.
You can see this space division technique being used again within the major shapes in this masterpiece by Canaletto. The contour of the buildings almost appears to pierce the sky.
Note the inclusion of the tall church tower on the right. This was deliberately included in order to further lock the two shapes of the sky and the mass of buildings together.